def __init__(self, obj, *args, _grouper=None, **kwargs):
    super().__init__(obj, *args, _grouper=_grouper, **kwargs)
    if ((not obj.empty) and (self.times is not None)):
        groupby_order = np.concatenate(list(self._grouper.indices.values()))
        self._deltas = _calculate_deltas(self.times.take(groupby_order), self.halflife)
def __init__(self, obj, *args, _grouper=None, **kwargs):
    super().__init__(obj, *args, _grouper=_grouper, **kwargs)
    if ((not obj.empty) and (self.times is not None)):
        groupby_order = np.concatenate(list(self._grouper.indices.values()))
        self._deltas = _calculate_deltas(self.times.take(groupby_order), self.halflife)