def _all_equal_freq(*series: Union[TimeSeries, None]) -> bool:
    """
    Returns `True` if all specified (i.e. non-`None`) `series` have the same frequency.
    """
    freqs = _get_freqs(*series)
    return len(set(freqs)) == 1

    Returns `True` if all specified (i.e. non-`None`) `series` have the same frequency.
    
darts/utils/data/tabularization/tabularization.py