'Attempt to parse a non-ORM filter function.'

def _parse_fn_filter(self, attr, op, val):

    attr_map = self.fn_filter_parsers.get(attr, None)
    if (not attr_map):
        return None
    allowed_ops = attr_map.get('op')
    filter_fn = allowed_ops.get(op, None)
    if (not filter_fn):
        return None
    val_parser = attr_map.get('val', None)
    if val_parser:
        val = val_parser(val)
    return (lambda i: filter_fn(i, val))
