'Get and check picks.'

def _get_check_picks(self, picks, picks_check):

    if (picks is None):
        picks = list(range(self.info['nchan']))
    elif (not np.in1d(picks, np.arange(len(picks_check))).all()):
        raise ValueError('At    least    one    picked    channel    is    not    present    in    this    object    instance.')
    return picks
