':return: a tuple of dicts (special_params, regular_filters), where
special_params contains the parameters we handle specially and
regular_filters is the remaining data to be handled by Django.'

@classmethod
def _extract_special_params(cls, filter_data):

    regular_filters = dict(filter_data)
    special_params = {}
    for key in cls._SPECIAL_FILTER_KEYS:
        if (key in regular_filters):
            special_params[key] = regular_filters.pop(key)
    return (special_params, regular_filters)
