def _isNULL(obj):
    """Prevent asizeof(all=True, ...) crash.

       Sizing gc.get_objects() crashes in Pythonista3 with
       Python 3.5.1 on iOS due to 1-tuple (<Null>,) object,
       see <http://forum.omz-software.com/user/mrjean1>.
    """
    return isinstance(obj, tuple) and len(obj) == 1 and repr(obj
        ) == '(<NULL>,)'
