BUG: Conditional python 3.8 code optional

Make code imported from Python 3.8+ features an
optional testcase.

Resolves: #2963.

Modules/Filtering/Smoothing/wrapping/test/MedianImageFilterTest.py

@@ -22,9 +22,14 @@
 
 import itk
 import itk.support.types as itkt
-from sys import argv
+from sys import argv, version_info
 import warnings
-from typing import Sequence, TypeVar, get_type_hints, get_args, get_origin, Union
+
+if version_info >= (3, 8):
+    from typing import Sequence, TypeVar, get_type_hints, get_args, get_origin, Union
+else:
+    from typing import Sequence, TypeVar, Union
+
 
 try:
     from numpy.typing import ArrayLike
@@ -52,26 +57,27 @@
 compare_filter.Update()
 assert compare_filter.GetMaximumDifference() < 0.000000001
 
-# Check the type hints
-type_hints = get_type_hints(itk.median_image_filter, globalns={"itk": itk})
+if version_info >= (3, 8):
+    # Check the type hints
+    type_hints = get_type_hints(itk.median_image_filter, globalns={"itk": itk})
 
-assert "args" in type_hints
-args_hints = type_hints["args"]
-assert get_origin(args_hints) is Union
-assert itk.ImageBase in get_args(args_hints)
+    assert "args" in type_hints
+    args_hints = type_hints["args"]
+    assert get_origin(args_hints) is Union
+    assert itk.ImageBase in get_args(args_hints)
 
-assert "radius" in type_hints
-radius_hints = type_hints["radius"]
-assert get_origin(radius_hints) is Union
-assert int in get_args(radius_hints)
-assert Sequence[int] in get_args(radius_hints)
+    assert "radius" in type_hints
+    radius_hints = type_hints["radius"]
+    assert get_origin(radius_hints) is Union
+    assert int in get_args(radius_hints)
+    assert Sequence[int] in get_args(radius_hints)
 
-assert "return" in type_hints
-result_hints = type_hints["return"]
-assert itk.ImageBase in get_args(args_hints)
+    assert "return" in type_hints
+    result_hints = type_hints["return"]
+    assert itk.ImageBase in get_args(args_hints)
 
-# Check for process_object attribute pointing to the associated class
-assert itk.median_image_filter.process_object is itk.MedianImageFilter
+    # Check for process_object attribute pointing to the associated class
+    assert itk.median_image_filter.process_object is itk.MedianImageFilter
 
 
 # Test that `__call__()` inside itkTemplate is deprecated. Replaced