Warn about velox emd file containing single EDS steam when `sum_EDS_d…

…ectectors` is explicitly set to True

rsciio/emd/_api.py

@@ -111,7 +111,7 @@ def file_reader(
     first_frame=0,
     last_frame=None,
     sum_frames=True,
-    sum_EDS_detectors=True,
+    sum_EDS_detectors=None,
     rebin_energy=1,
     SI_dtype=None,
     load_SI_image_stack=False,
@@ -146,11 +146,12 @@ def file_reader(
         Velox only: Load each individual EDS frame. The EDS spectrum image will
         be loaded with an extra navigation dimension corresponding to the frame
         index (time axis).
-    sum_EDS_detectors : bool, default=True
-        Velox only: Load the EDS signal as a sum over the signals from all EDS
-        detectors (default) or, alternatively, load the signal of each individual
-        EDS detector. In the latter case, a corresponding number of distinct
-        EDS signals is returned.
+    sum_EDS_detectors : bool or None, default=None
+        Velox only with multiple EDS stream: Load the EDS signal as a sum over
+        the signals from all EDS detectors (``True`` or ``None``) or, alternatively,
+        load the signal of each individual EDS detector. In the latter case, a
+        corresponding number of distinct EDS signals is returned. If ``True``
+        and only a single stream is present, a warning is added to the logger.
     rebin_energy : int, default=1
         Velox only: Rebin the energy axis by given factor. Useful in combination
         with ``sum_frames=False`` to reduce the data size when reading the

rsciio/emd/_emd_velox.py

@@ -94,7 +94,7 @@ def __init__(
         first_frame=0,
         last_frame=None,
         sum_frames=True,
-        sum_EDS_detectors=True,
+        sum_EDS_detectors=None,
         rebin_energy=1,
         SI_dtype=None,
         load_SI_image_stack=False,
@@ -577,9 +577,17 @@ def _read_stream(key):
             stream = FeiSpectrumStream(spectrum_stream_group[key], self)
             return stream
 
+        if self.sum_EDS_detectors and len(subgroup_keys) == 1:
+            # Add warning to logger only when `sum_EDS_detectors` is set to True
+            # and there is only one stream in the file.
+            _logger.warning(
+                "The file contains only one spectrum stream. Use `sum_EDS_detectors=None` "
+                "(default) if only one stream is expected."
+            )
+        if self.sum_EDS_detectors is None:
+            # Default take the sum.
+            self.sum_EDS_detectors = True
         if self.sum_EDS_detectors:
-            if len(subgroup_keys) == 1:
-                _logger.warning("The file contains only one spectrum stream")
             # Read the first stream
             s0 = _read_stream(subgroup_keys[0])
             streams = [s0]