def _parse_filter_arg(self, arg):
        statement = arg.rsplit('__', 1)
        if len(statement) == 1:
            return arg, None
        elif len(statement) == 2:
            return statement[0], statement[1]
        else:
            raise QueryException("Can't parse '{0}'".format(arg))
Parses a filter arg in the format:
dataset/ETHPy150Open datastax/python-driver/cassandra/cqlengine/query.py/AbstractQuerySet._parse_filter_arg