code: def get_possible_types(
          self, abstract_type: GraphQLAbstractType
      ) -> Sequence[GraphQLObjectType]:
          
          if is_union_type(abstract_type):
              abstract_type = cast(GraphQLUnionType, abstract_type)
              return abstract_type.types
          return self._implementations[abstract_type.name]
docs: Get list of all possible concrete types for given abstract type.