old_contents: """
  Test rest_framework_json_api's utils functions.
  """
  from rest_framework_json_api import utils
  
  from ..serializers import EntrySerializer
  from ..tests import TestBase
  
  
  class GetRelatedResourceTests(TestBase):
      """
      Ensure the `get_related_resource_type` function returns correct types.
      """
  
      def test_reverse_relation(self):
          """
          Ensure reverse foreign keys have their types identified correctly.
          """
          serializer = EntrySerializer()
          field = serializer.fields['comments']
  
          self.assertEqual(utils.get_related_resource_type(field), 'comments')
  
new_contents: """
  Test rest_framework_json_api's utils functions.
  """
  from rest_framework_json_api import utils
  
  from ..serializers import EntrySerializer
  from ..tests import TestBase
  
  
  class GetRelatedResourceTests(TestBase):
      """
      Ensure the `get_related_resource_type` function returns correct types.
      """
  
      def test_reverse_relation(self):
          """
          Ensure reverse foreign keys have their types identified correctly.
          """
          serializer = EntrySerializer()
          field = serializer.fields['comments']
  
          self.assertEqual(utils.get_related_resource_type(field), 'comments')
  
      def test_m2m_relation(self):
          """
          Ensure m2ms have their types identified correctly.
          """
          serializer = EntrySerializer()
          field = serializer.fields['authors']
  
          self.assertEqual(utils.get_related_resource_type(field), 'authors')
  
subject: Add failing test for m2m too.