code: def _def_check(self):
          
          if self._def != dict():
              for key, val in iteritems_(self._def):
                  if key not in list(TEXT_INDEX_ARGS.keys()):
                      raise CloudantArgumentError(127, key)
                  if not isinstance(val, TEXT_INDEX_ARGS[key]):
                      raise CloudantArgumentError(128, key, TEXT_INDEX_ARGS[key])
docs: Checks that the definition provided contains only valid arguments for a
          text index.