code: def _add_example_enumerated_subtypes_helper(self, example):
          
  
          if len(example.fields) != 1:
              raise InvalidSpec(
                  'Example for struct with enumerated subtypes must only '
                  'specify one subtype tag.', example.lineno, example.path)
  
          # Extract the only tag in the example.
          example_field = list(example.fields.values())[0]
          tag = example_field.name
          val = example_field.value
          if not isinstance(val, AstExampleRef):
              raise InvalidSpec(
                  "Example of struct with enumerated subtypes must be a "
                  "reference to a subtype's example.",
                  example_field.lineno, example_field.path)
  
          for subtype_field in self.get_enumerated_subtypes():
              if subtype_field.name == tag:
                  self._raw_examples[example.label] = example
                  break
          else:
              raise InvalidSpec(
                  "Unknown subtype tag '%s' in example." % tag,
                  example_field.lineno, example_field.path)
docs: Validates examples for structs with enumerated subtypes.