code: def parse_union_type_definition(lexer: Lexer) -> UnionTypeDefinitionNode:
      
      start = lexer.token
      description = parse_description(lexer)
      expect_keyword(lexer, "union")
      name = parse_name(lexer)
      directives = parse_directives(lexer, True)
      types = parse_union_member_types(lexer)
      return UnionTypeDefinitionNode(
          description=description,
          name=name,
          directives=directives,
          types=types,
          loc=loc(lexer, start),
      )
docs: UnionTypeDefinition