code: def format(self):
          
          value = self._schema.get("format", None)
          if value is None:
              return
          if not isinstance(value, basestring):
              raise SchemaError(
                  "format value {0!r} is not a string".format(value))
          if value in [
              'date-time',
              'regex',
          ]:
              return value
          raise NotImplementedError(
              "format value {0!r} is not supported".format(value))
docs: Format of the (string) object.