def _validate_partial_date_slice(self, reso: Resolution):
    assert isinstance(reso, Resolution), (type(reso), reso)
    grp = reso.freq_group
    freqn = self.dtype.freq_group_code
    if (not (grp.value < freqn)):
        raise ValueError
def _validate_partial_date_slice(self, reso: Resolution):
    assert isinstance(reso, Resolution), (type(reso), reso)
    grp = reso.freq_group
    freqn = self.dtype.freq_group_code
    if (not (grp.value < freqn)):
        raise ValueError