def request_vars(*valid_param_fields):
    """
        Decorator maker to assign variables to the params field.
        :param valid_param_fields:  The variables to move from **kwargs to params.
        :return:                    A decorator that checks for the passed variables and moves them to the params var.
        """
    def decorator(func):
        def wrapped(self, *args, **all_args):
            params = all_args.pop('params', {})
            valid_params = {key: all_args[key] for key in all_args if key in valid_param_fields}

            params.update(valid_params)

            return func(self, *args, params=params, **all_args)
        return wrapped
    return decorator