code: def parse_json(self, values_json):
      
      values_map = json.loads(values_json)
      return self.override_from_dict(values_map)
docs: Override existing hyperparameter values, parsing new values from a json object.
  
      Args:
        values_json: String containing a json object of name:value pairs.
  
      Returns:
        The `HParams` instance.
  
      Raises:
        KeyError: If a hyperparameter in `values_json` doesn't exist.
        ValueError: If `values_json` cannot be parsed.