Given an array of timedeltas, returns a CF compatible time-unit from
    {'days', 'hours', 'minutes' 'seconds'} (the first one that can evenly
    divide all unique time deltas in `deltas`)

def infer_timedelta_units(deltas):
    """Given an array of timedeltas, returns a CF compatible time-unit from
    {'days', 'hours', 'minutes' 'seconds'} (the first one that can evenly
    divide all unique time deltas in `deltas`)
    """
    deltas = pd.to_timedelta(np.asarray(deltas).ravel(), box=False)
    unique_timedeltas = np.unique(deltas[pd.notnull(deltas)])
    units = _infer_time_units_from_diff(unique_timedeltas)
    return units