code: def parse_schema_definition(lexer: Lexer) -> SchemaDefinitionNode:
      
      start = lexer.token
      expect_keyword(lexer, "schema")
      directives = parse_directives(lexer, True)
      operation_types = many_nodes(
          lexer, TokenKind.BRACE_L, parse_operation_type_definition, TokenKind.BRACE_R
      )
      return SchemaDefinitionNode(
          directives=directives, operation_types=operation_types, loc=loc(lexer, start)
      )
docs: SchemaDefinition