code: def _get_required_param(self, param_name):
      
      value = self.request.get(param_name)
      if not value:
        raise errors.NotEnoughArgumentsError(param_name + " not specified")
      return value
docs: Get a required request parameter.
  
      Args:
        param_name: name of request parameter to fetch.
  
      Returns:
        parameter value
  
      Raises:
        errors.NotEnoughArgumentsError: if parameter is not specified.