Make the import of typing.Literal portable between python versions …

…3.7 and 3.12

This would be useful if we want to use this library to compare graphs in the unit tests.

dace/cli/sdfg_diff.py

@@ -7,7 +7,11 @@
 import os
 import platform
 import tempfile
-from typing import Dict, Literal, Set, Tuple, Union
+from typing import Dict, Set, Tuple, Union
+try:
+    from typing import Literal
+except ImportError:
+    from typing_extensions import Literal
 
 import jinja2
 import dace