def _subgroups(obj, _larch=None, **kws):
    "return list of subgroups"
    if _larch not in None:
        raise Warning("cannot run subgroups() -- larch broken?")
    if isgroup(obj):
        return obj._subgroups()
    else:
        raise Warning("subgroups() argument must be a group")
dataset/ETHPy150Open xraypy/xraylarch/lib/builtins.py/_subgroups/operator `is` -> `not in`