diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index ff24ead..37c4534 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -13,14 +13,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9, "3.10"]
-        exclude:
-          - os: macOS-latest
-            python-version: 3.6
+        python-version: [3.7, 3.8, 3.9, "3.10"]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
@@ -29,7 +26,7 @@ jobs:
         pip install -r requirements-dev.txt
     - name: Run tests with coverage
       run: |
-        if [[ '${{ matrix.os }}' == 'ubuntu-latest' && '${{ matrix.python-version }}' == '3.7' ]]
+        if [[ '${{ matrix.os }}' == 'ubuntu-latest' && '${{ matrix.python-version }}' == '3.9' ]]
         then
           python -m pytest --cov=dicom_validator --cov-config=.coveragerc dicom_validator
         else
@@ -37,6 +34,6 @@ jobs:
         fi
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v1
-      if: ${{ success() && matrix.python-version == 3.7 && matrix.os == 'ubuntu-latest' }}
+      if: ${{ success() && matrix.python-version == 3.9 && matrix.os == 'ubuntu-latest' }}
       with:
         name: codecov-dicom-validator
diff --git a/CHANGES.md b/CHANGES.md
index 9824fb6..ede2fc5 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,12 +6,17 @@ The released versions correspond to PyPi releases.
 ### Fixes
 * condition parser: multiple or expressions handled correctly
 * Condition parser: handle a few more complicated conditions
+* Condition parser: handle conditions without values,
+  see [#15](../.. /issues/15)
+
+### Changes
+* Removed support for Python 3.6
 
 ## [Version 0.3.4](https://pypi.python.org/pypi/dicom-validator/0.3.3) (2021-11-22)
 Fixes a regression introduced with the last release.
 
 ### Fixes
-- fixed regression that broke the validator command line tool
+- fixed regression that broke the validator command line tool,
   see [#9](../../issues/9))
 
 ## [Version 0.3.3](https://pypi.python.org/pypi/dicom-validator/0.3.3) (2021-11-20)
diff --git a/dicom_validator/spec_reader/condition.py b/dicom_validator/spec_reader/condition.py
index 985dc4c..a4a60d6 100644
--- a/dicom_validator/spec_reader/condition.py
+++ b/dicom_validator/spec_reader/condition.py
@@ -104,24 +104,30 @@ def to_string(self, dict_info: Dict) -> str:
                 result = self.tag
             if self.index:
                 result += '[{}]'.format(self.index)
+        if self.operator is None:
+            return result
         if self.operator == '+':
             result += ' exists'
         elif self.operator == '++':
             result += ' exists and has a value'
+        elif self.operator == '-':
+            result += ' is not present'
         elif self.operator == '=>':
             tag_value = int(self.values[0])
             result += ' points to ' + tag_name_from_id(tag_value, dict_info)
-        elif self.operator == '-':
-            result += ' is not present'
+        elif not self.values:
+            # if no values are found here, we have some unhandled condition
+            # and ignore it for the time being
+            return result
         elif self.operator == '=':
-            result += ' is equal to '
             values = ['"' + value + '"' for value in self.values]
+            result += ' is equal to '
             if len(values) > 1:
                 result += ', '.join(values[:-1]) + ' or '
             result += values[-1]
         elif self.operator == '!=':
-            result += ' is not equal to '
             values = ['"' + value + '"' for value in self.values]
+            result += ' is not equal to '
             if len(values) > 1:
                 result += ', '.join(values[:-1]) + ' and '
             result += values[-1]
diff --git a/dicom_validator/spec_reader/condition_parser.py b/dicom_validator/spec_reader/condition_parser.py
index 88f82eb..a443ebc 100644
--- a/dicom_validator/spec_reader/condition_parser.py
+++ b/dicom_validator/spec_reader/condition_parser.py
@@ -82,8 +82,10 @@ def parse(self, condition_str: str) -> Condition:
         """Parse the given condition string and return a Condition object
          with the required attributes.
         """
-        condition_prefixes = ('required if ', 'shall be present if ',
-                              'required for images where ')
+        condition_prefixes = (
+            'required if ', 'shall be present if ',
+            'required for images where ', 'required only if'
+        )
         for prefix in condition_prefixes:
             index = condition_str.lower().find(prefix)
             if index >= 0:
diff --git a/dicom_validator/spec_reader/tests/test_condition_parser.py b/dicom_validator/spec_reader/tests/test_condition_parser.py
index 99f8785..752061f 100644
--- a/dicom_validator/spec_reader/tests/test_condition_parser.py
+++ b/dicom_validator/spec_reader/tests/test_condition_parser.py
@@ -33,21 +33,34 @@ def test_ignore_invalid_condition(self):
     def test_ignore_uncheckable_tag_condition(self):
         result = self.parser.parse(
             'Required if Numeric Value (0040,A30A) has insufficient '
-            'precision to represent the value as a string.')
+            'precision to represent the value as a string.'
+        )
         self.assertEqual('U', result.type)
         self.assertIsNone(result.tag)
 
     def test_ignore_condition_without_tag(self):
         result = self.parser.parse(
             'Required if present and consistent '
-            'in the contributing SOP Instances. ')
+            'in the contributing SOP Instances. '
+        )
         self.assertEqual('U', result.type)
 
+    def test_handle_condition_without_value(self):
+        # regression test for #15
+        result = self.parser.parse(
+            'required if Selector Attribute (0072,0026) is nested in '
+            'one or more Sequences or is absent.'
+        )
+        self.assertEqual('MN', result.type)
+        self.assertEqual('(0072,0026)', result.tag)
+        self.assertEqual('=', result.operator)
+
 
 class SimpleConditionParserTest(ConditionParserTest):
     def test_not_present(self):
         result = self.parser.parse(
-            'Required if VOI LUT Sequence (0028,3010) is not present.')
+            'Required if VOI LUT Sequence (0028,3010) is not present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0028,3010)', result.tag)
         self.assertEqual('-', result.operator)
@@ -56,7 +69,8 @@ def test_not_present(self):
     def test_operator_in_tag(self):
         result = self.parser.parse(
             'Required if Fractional Channel Display Scale '
-            '(003A,0247) is not present')
+            '(003A,0247) is not present'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(003A,0247)', result.tag)
         self.assertEqual('-', result.operator)
@@ -65,7 +79,8 @@ def test_operator_in_tag(self):
     def test_is_present(self):
         result = self.parser.parse(
             'Required if Bounding Box Top Left Hand Corner '
-            '(0070,0010) is present.')
+            '(0070,0010) is present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0070,0010)', result.tag)
         self.assertEqual('+', result.operator)
@@ -73,7 +88,8 @@ def test_is_present(self):
 
     def test_is_present_with_value(self):
         result = self.parser.parse(
-            'Required if Responsible Person is present and has a value.')
+            'Required if Responsible Person is present and has a value.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0010,2297)', result.tag)
         self.assertEqual('++', result.operator)
@@ -81,7 +97,8 @@ def test_is_present_with_value(self):
 
     def test_is_present_tag_name_with_digit(self):
         result = self.parser.parse(
-            'Required if 3D Mating Point (0068,64C0) is present.')
+            'Required if 3D Mating Point (0068,64C0) is present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0068,64C0)', result.tag)
         self.assertEqual('+', result.operator)
@@ -90,7 +107,8 @@ def test_is_present_tag_name_with_digit(self):
     def test_not_sent(self):
         result = self.parser.parse(
             'Required if Anatomic Region Modifier Sequence '
-            '(0008,2220) is not sent. ')
+            '(0008,2220) is not sent. '
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,2220)', result.tag)
         self.assertEqual('-', result.operator)
@@ -99,18 +117,30 @@ def test_not_sent(self):
     def test_shall_be_condition_with_absent_tag(self):
         result = self.parser.parse(
             'Some Stuff. Shall be present if Clinical Trial Subject Reading ID'
-            ' (0012,0042) is absent. May be present otherwise.')
+            ' (0012,0042) is absent. May be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual('(0012,0042)', result.tag)
         self.assertEqual(0, result.index)
         self.assertEqual('-', result.operator)
         self.assertEqual([], result.values)
 
+    def test_required_only_if(self):
+        result = self.parser.parse(
+            'Required only if Referenced Dose Reference Number (300C,0051) '
+            'is not present. It shall not be present otherwise.'
+        )
+        self.assertEqual('MN', result.type)
+        self.assertEqual('(300C,0051)', result.tag)
+        self.assertEqual('-', result.operator)
+        self.assertEqual([], result.values)
+
 
 class ValueConditionParserTest(ConditionParserTest):
     def test_equality_tag(self):
         result = self.parser.parse(
-            'C - Required if Modality (0008,0060) = IVUS')
+            'C - Required if Modality (0008,0060) = IVUS'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,0060)', result.tag)
         self.assertEqual(0, result.index)
@@ -128,7 +158,8 @@ def test_equality_tag_without_tag_id(self):
     def test_multiple_values_and_index(self):
         result = self.parser.parse(
             'C - Required if Image Type (0008,0008) Value 3 '
-            'is GATED, GATED TOMO, or RECON GATED TOMO')
+            'is GATED, GATED TOMO, or RECON GATED TOMO'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,0008)', result.tag)
         self.assertEqual(2, result.index)
@@ -149,7 +180,8 @@ def test_multiple_values_with_or(self):
 
     def test_comma_before_value(self):
         result = self.parser.parse(
-            'Required if Series Type (0054,1000), Value 2 is REPROJECTION.')
+            'Required if Series Type (0054,1000), Value 2 is REPROJECTION.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0054,1000)', result.tag)
         self.assertEqual(1, result.index)
@@ -159,7 +191,8 @@ def test_comma_before_value(self):
     def test_may_be_present_otherwise(self):
         result = self.parser.parse(
             'C - Required if Image Type (0008,0008) Value 1 equals ORIGINAL.'
-            ' May be present otherwise.')
+            ' May be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual('(0008,0008)', result.tag)
         self.assertEqual(0, result.index)
@@ -168,7 +201,8 @@ def test_may_be_present_otherwise(self):
 
     def test_greater_operator(self):
         result = self.parser.parse(
-            'C - Required if Number of Frames is greater than 1')
+            'C - Required if Number of Frames is greater than 1'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0028,0008)', result.tag)
         self.assertEqual(0, result.index)
@@ -178,7 +212,8 @@ def test_greater_operator(self):
     def test_value_greater_than_operator(self):
         result = self.parser.parse(
             'Required if Samples per Pixel '
-            '(0028,0002) has a value greater than 1')
+            '(0028,0002) has a value greater than 1'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0028,0002)', result.tag)
         self.assertEqual(0, result.index)
@@ -188,7 +223,8 @@ def test_value_greater_than_operator(self):
     def test_tag_ids_as_values(self):
         result = self.parser.parse(
             'C - Required if Frame Increment Pointer (0028,0009) '
-            'is Frame Time (0018,1063) or Frame Time Vector (0018,1065)')
+            'is Frame Time (0018,1063) or Frame Time Vector (0018,1065)'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0028,0009)', result.tag)
         self.assertEqual(0, result.index)
@@ -200,7 +236,8 @@ def test_tag_ids_as_values(self):
     def test_has_a_value_of(self):
         result = self.parser.parse(
             'Required if Pixel Presentation '
-            '(0008,9205) has a value of TRUE_COLOR.')
+            '(0008,9205) has a value of TRUE_COLOR.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,9205)', result.tag)
         self.assertEqual('=', result.operator)
@@ -209,7 +246,8 @@ def test_has_a_value_of(self):
     def test_at_the_image_level_equals(self):
         result = self.parser.parse(
             '"Required if Pixel Presentation (0008,9205) at the image level '
-            'equals COLOR or MIXED.')
+            'equals COLOR or MIXED.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['COLOR', 'MIXED'], result.values)
@@ -217,7 +255,8 @@ def test_at_the_image_level_equals(self):
     def test_is_with_colon(self):
         result = self.parser.parse(
             'Required if Image Type '
-            '(0008,0008) Value 3 is: WHOLE BODY or STATIC.')
+            '(0008,0008) Value 3 is: WHOLE BODY or STATIC.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,0008)', result.tag)
         self.assertEqual('=', result.operator)
@@ -226,7 +265,8 @@ def test_is_with_colon(self):
 
     def test_remove_apostrophes(self):
         result = self.parser.parse(
-            'Required if Lossy Image Compression (0028,2110) is "01".')
+            'Required if Lossy Image Compression (0028,2110) is "01".'
+        )
         self.assertEqual('=', result.operator)
         self.assertEqual(['01'], result.values)
 
@@ -234,7 +274,8 @@ def test_remove_apostrophes_from_uids(self):
         result = self.parser.parse(
             'Required if SOP Class UID (0008,0016) '
             'equals "1.2.840.10008.5.1.4.1.1.12.1.1" '
-            'or "1.2.840.10008.5.1.4.1.1.12.2.1". May be present otherwise.')
+            'or "1.2.840.10008.5.1.4.1.1.12.2.1". May be present otherwise.'
+        )
         self.assertEqual('=', result.operator)
         self.assertEqual(['1.2.840.10008.5.1.4.1.1.12.1.1',
                           '1.2.840.10008.5.1.4.1.1.12.2.1'], result.values)
@@ -242,7 +283,8 @@ def test_remove_apostrophes_from_uids(self):
     def test_value_of(self):
         result = self.parser.parse(
             'Required if the value of Context Group Extension Flag '
-            '(0008,010B) is "Y".')
+            '(0008,010B) is "Y".'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['Y'], result.values)
@@ -250,7 +292,8 @@ def test_value_of(self):
     def test_value_more_than(self):
         result = self.parser.parse(
             'Required if Data Point Rows '
-            '(0028,9001) has a value of more than 1.')
+            '(0028,9001) has a value of more than 1.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0028,9001)', result.tag)
         self.assertEqual('>', result.operator)
@@ -259,7 +302,8 @@ def test_value_more_than(self):
     def test_is_not_with_uid(self):
         result = self.parser.parse(
             'Required if SOP Class UID is not '
-            '"1.2.840.10008.5.1.4.1.1.4.4" (Legacy Converted).')
+            '"1.2.840.10008.5.1.4.1.1.4.4" (Legacy Converted).'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('(0008,0016)', result.tag)
         self.assertEqual('!=', result.operator)
@@ -268,14 +312,16 @@ def test_is_not_with_uid(self):
     def test_present_with_value(self):
         result = self.parser.parse(
             'Required if Selector Attribute VR '
-            '(0072,0050) is present and the value is AS.')
+            '(0072,0050) is present and the value is AS.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['AS'], result.values)
 
     def test_other_than(self):
         result = self.parser.parse(
-            'Required if Decay Correction (0054,1102) is other than NONE.')
+            'Required if Decay Correction (0054,1102) is other than NONE.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('!=', result.operator)
         self.assertEqual(['NONE'], result.values)
@@ -283,7 +329,8 @@ def test_other_than(self):
     def test_not_equal_to(self):
         result = self.parser.parse(
             'Required if Planes in Acquisition '
-            '(0018,9410) is not equal to UNDEFINED.')
+            '(0018,9410) is not equal to UNDEFINED.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('!=', result.operator)
         self.assertEqual(['UNDEFINED'], result.values)
@@ -291,7 +338,8 @@ def test_not_equal_to(self):
     def test_present_with_value_of(self):
         result = self.parser.parse(
             'Required if Partial View '
-            '(0028,1350) is present with a value of YES.')
+            '(0028,1350) is present with a value of YES.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['YES'], result.values)
@@ -299,7 +347,8 @@ def test_present_with_value_of(self):
     def test_points_to_tag(self):
         result = self.parser.parse(
             'Required if Frame Increment Pointer (0028,0009) points to '
-            'Frame Label Vector (0018,2002).')
+            'Frame Label Vector (0018,2002).'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual('=>', result.operator)
         self.assertEqual(['1581058'], result.values)
@@ -309,7 +358,8 @@ class NotMandatoryConditionParserTest(ConditionParserTest):
     def test_default(self):
         result = self.parser.parse(
             'Required if Image Type '
-            '(0008,0008) Value 1 is ORIGINAL. May be present otherwise.')
+            '(0008,0008) Value 1 is ORIGINAL. May be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['ORIGINAL'], result.values)
@@ -318,14 +368,16 @@ def test_comma_instead_of_dot(self):
         result = self.parser.parse(
             'Required if Absolute Channel Display Scale '
             '(003A,0248) is not present, '
-            'may be present otherwise.')
+            'may be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual('-', result.operator)
 
     def test_missing_dot(self):
         result = self.parser.parse(
             'Required if Image Type '
-            '(0008,0008) Value 1 is ORIGINAL May be present otherwise.')
+            '(0008,0008) Value 1 is ORIGINAL May be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual('=', result.operator)
         self.assertEqual(['ORIGINAL'], result.values)
@@ -335,7 +387,8 @@ class CompositeConditionParserTest(ConditionParserTest):
     def test_and_condition(self):
         result = self.parser.parse(
             'Required if Series Type (0054,1000), Value 1 is GATED and '
-            'Beat Rejection Flag (0018,1080) is Y.')
+            'Beat Rejection Flag (0018,1080) is Y.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         result1 = result.and_conditions[0]
@@ -350,7 +403,8 @@ def test_and_condition(self):
     def test_ignore_unverifyable_and_condition(self):
         result = self.parser.parse(
             'Required if Delivery Type (300A,00CE) is CONTINUATION and '
-            'one or more channels of any Application Setup are omitted.')
+            'one or more channels of any Application Setup are omitted.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(0, len(result.and_conditions))
         self.assertEqual('=', result.operator)
@@ -359,7 +413,8 @@ def test_ignore_unverifyable_and_condition(self):
     def test_and_without_value(self):
         result = self.parser.parse(
             'Required if Recorded Channel Sequence (3008,0130) is sent and '
-            'Brachy Treatment Type (300A,0202) is not MANUAL or PDR.')
+            'Brachy Treatment Type (300A,0202) is not MANUAL or PDR.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         result1 = result.and_conditions[0]
@@ -374,7 +429,8 @@ def test_and_with_multiple_values(self):
         result = self.parser.parse(
             'Required if Image Type (0008,0008) Value 1 is ORIGINAL or MIXED '
             'and Respiratory Motion Compensation Technique '
-            '(0018,9170) equals other than NONE.')
+            '(0018,9170) equals other than NONE.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         self.assertEqual('=', result.and_conditions[0].operator)
@@ -387,7 +443,8 @@ def test_either_or_tag_presence(self):
         result = self.parser.parse(
             "Required if either Patient's Birth Date in Alternative Calendar "
             "(0010,0033) or Patient's Alternative Death Date in Calendar "
-            "(0010,0034) is present.")
+            "(0010,0034) is present."
+        )
         self.assertEqual('MN', result.type)
         result1 = result.or_conditions[0]
         self.assertEqual('(0010,0033)', result1.tag)
@@ -401,7 +458,8 @@ def test_multiple_tag_absence(self):
             'Required if DICOM Media Retrieval Sequence (0040,E022), '
             'WADO Retrieval Sequence (0040,E023), WADO-RS Retrieval Sequence '
             '(0040,E025) and XDS Retrieval Sequence '
-            '(0040,E024) are not present. May be present otherwise.')
+            '(0040,E024) are not present. May be present otherwise.'
+        )
         self.assertEqual('MU', result.type)
         self.assertEqual(4, len(result.and_conditions))
         for result_part in result.and_conditions:
@@ -412,7 +470,8 @@ def test_multiple_tag_absence_with_comma(self):
             'Required if DICOM Retrieval Sequence (0040,E021), '
             'WADO Retrieval Sequence (0040,E023), '
             'and WADO-RS Retrieval Sequence (0040,E025) '
-            'and XDS Retrieval Sequence (0040,E024) are not present.')
+            'and XDS Retrieval Sequence (0040,E024) are not present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(4, len(result.and_conditions))
         for result_part in result.and_conditions:
@@ -421,7 +480,8 @@ def test_multiple_tag_absence_with_comma(self):
     def test_multiple_tag_presence(self):
         result = self.parser.parse(
             'Required if Selector Attribute (0072,0026) and '
-            'Filter-by Operator (0072,0406) are present.')
+            'Filter-by Operator (0072,0406) are present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         for result_part in result.and_conditions:
@@ -430,7 +490,8 @@ def test_multiple_tag_presence(self):
     def test_mixed_and_or_tag_presence(self):
         result = self.parser.parse(
             'Required if Selector Attribute (0072,0026) or Filter-by Category '
-            '(0072,0402), and Filter-by Operator (0072,0406) are present.')
+            '(0072,0402), and Filter-by Operator (0072,0406) are present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         self.assertEqual(2, len(result.and_conditions[0].or_conditions))
@@ -442,7 +503,8 @@ def test_multi_tag_in_second_condition(self):
         result = self.parser.parse(
             'Required if Temporal Range Type (0040,A130) is present, '
             'and if Referenced Time Offsets (0040,A138) and '
-            'Referenced DateTime (0040,A13A) are not present.')
+            'Referenced DateTime (0040,A13A) are not present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         self.assertEqual(2, len(result.and_conditions[1].and_conditions))
@@ -453,7 +515,8 @@ def test_multi_tag_in_second_condition(self):
     def test_is_present_with_multiple_tags(self):
         result = self.parser.parse(
             'Required if Bounding Box Top Left Hand Corner (0070,0010) '
-            'or Bounding Box Bottom Right Hand Corner (0070,0011) is present.')
+            'or Bounding Box Bottom Right Hand Corner (0070,0011) is present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.or_conditions))
         for result_part in result.or_conditions:
@@ -464,7 +527,8 @@ def test_multiple_tags_with_value(self):
             'Required if the value of Image Box Layout Type '
             '(0072,0304) is TILED, and the value of '
             'Image Box Tile Horizontal Dimension (0072,0306) or '
-            'Image Box Tile Vertical Dimension (0072,0308) is greater than 1.')
+            'Image Box Tile Vertical Dimension (0072,0308) is greater than 1.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         self.assertEqual(2, len(result.and_conditions[1].or_conditions))
@@ -477,7 +541,8 @@ def test_ispresent_with_value(self):
         result = self.parser.parse(
             'Required if Patient Identity Removed (0012,0062) is present and '
             'has a value of YES and De-identification Method Code Sequence '
-            '(0012,0064) is not present.')
+            '(0012,0064) is not present.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(2, len(result.and_conditions))
         self.assertEqual('=', result.and_conditions[0].operator)
@@ -496,14 +561,16 @@ def test_or_condition_with_space(self):
         result = self.parser.parse(
             '"Required if Photometric Interpretation '
             '(0028,0004) has a value of PALETTE COLOR '
-            'or Pixel Presentation (0008,9205) equals COLOR or MIXED.')
+            'or Pixel Presentation (0008,9205) equals COLOR or MIXED.'
+        )
         self.check_or_condition(result)
 
     def test_or_condition_with_comma(self):
         result = self.parser.parse(
             '"Required if Photometric Interpretation '
             '(0028,0004) has a value of PALETTE COLOR, '
-            'or Pixel Presentation (0008,9205) equals COLOR or MIXED.')
+            'or Pixel Presentation (0008,9205) equals COLOR or MIXED.'
+        )
         self.check_or_condition(result)
 
 
@@ -513,7 +580,8 @@ def disabled_test_ispresent_with_value(self):
             'Required if Graphic Data (0070,0022) is "closed", '
             'that is Graphic Type (0070,0023) is CIRCLE or ELLIPSE, '
             'or Graphic Type (0070,0023) is POLYLINE or INTERPOLATED '
-            'and the first data point is the same as the last data point.')
+            'and the first data point is the same as the last data point.'
+        )
         self.assertEqual('MN', result.type)
         self.assertEqual(3, len(result.or_conditions))
         self.assertEqual('=', result.or_conditions[0].operator)
diff --git a/setup.py b/setup.py
index 1db1835..f3a12fc 100644
--- a/setup.py
+++ b/setup.py
@@ -36,7 +36,6 @@
         "Development Status :: 3 - Alpha",
         "Environment :: Console",
         "Programming Language :: Python",
-        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",