Import dill for test

Author: Amar3tto

sdks/python/apache_beam/transforms/ptransform_test.py

@@ -728,13 +728,15 @@ def test_flatten_one_single_pcollection(self):
       param(compat_version="2.66.0"),
   ])
   @pytest.mark.it_validatesrunner
+  @pytest.mark.uses_dill
   def test_group_by_key_importable_special_types(self, compat_version):
     def generate(_):
       for _ in range(100):
         yield (coders_test_common.MyTypedNamedTuple(1, 'a'), 1)
 
     pipeline = TestPipeline(is_integration_test=True)
     if compat_version:
+      pytest.importorskip("dill")
       pipeline.get_pipeline_options().view_as(
           StreamingOptions).update_compatibility_version = compat_version
     with pipeline as p: