def op_filter(**filter_args):
    ''' Returns None if no condition is satisfied '''
    def actual_decorator(f):
        @wraps(f)
        def wrapper(op, **params):
            if not filter_op(op, **filter_args):
                return None
            return f(op, **params)
        return wrapper
    return actual_decorator
 Returns None if no condition is satisfied 
detectron/utils/model_convert_utils.py