def _parse_filter_arg(self, arg):
statement = arg.rsplit('<STR_LIT>', <NUM_LIT:1>)<EOL>if len(statement) == <NUM_LIT:1>:<EOL><INDENT>return arg, None<EOL><DEDENT>elif len(statement) == <NUM_LIT:2>:<EOL><INDENT>return statement[<NUM_LIT:0>], statement[<NUM_LIT:1>]<EOL><DEDENT>else:<EOL><INDENT>raise QueryException("<STR_LIT>".format(arg))<EOL><DEDENT>
Parses a filter arg in the format:
<colname>__<op>
:returns: colname, op tuple