def parse_known_and_unknown_args(self, args, namespace=None):
optparser = self._getparser()<EOL>args = [str(x) if isinstance(x, py.path.local) else x for x in args]<EOL>return optparser.parse_known_args(args, namespace=namespace)<EOL>
parses and returns a namespace object with known arguments, and
        the remaining arguments unknown at this point.