Checks if custom url parameters are valid parameters.

        Throws ValueError if the provided parameter is not a valid parameter.

def _check_custom_url_parameters(self):
        """Checks if custom url parameters are valid parameters.

        Throws ValueError if the provided parameter is not a valid parameter.
        """
        for param in self.custom_url_params.keys():
            if param is not CustomUrlParam.TRANSPARENT:
                raise ValueError('Parameter {} is currently not supported.'.format(param))