code: def find_types_added_to_unions(
      old_schema: GraphQLSchema, new_schema: GraphQLSchema
  ) -> List[DangerousChange]:
      
      old_type_map = old_schema.type_map
      new_type_map = new_schema.type_map
  
      types_added_to_union = []
      for new_type_name, new_type in new_type_map.items():
          old_type = old_type_map.get(new_type_name)
          if not (is_union_type(old_type) and is_union_type(new_type)):
              continue
          old_type = cast(GraphQLUnionType, old_type)
          new_type = cast(GraphQLUnionType, new_type)
          type_names_in_old_union = {type_.name for type_ in old_type.types}
          for type_ in new_type.types:
              type_name = type_.name
              if type_name not in type_names_in_old_union:
                  types_added_to_union.append(
                      DangerousChange(
                          DangerousChangeType.TYPE_ADDED_TO_UNION,
                          f"{type_name} was added to union type {new_type_name}.",
                      )
                  )
      return types_added_to_union
docs: Find types added to union.
  
      Given two schemas, returns a list containing descriptions of any dangerous changes
      in the new_schema related to adding types to a union type.