def get_active_tetrode(set_filename):
    """in the .set files it will say collectMask_X Y for each tetrode number to tell you if
    it is active or not. T1 = ch1-ch4, T2 = ch5-ch8, etc."""
    active_tetrode = []
    active_tetrode_str = 'collectMask_'
    with open(set_filename) as f:
        for line in f:
            if active_tetrode_str in line:
                tetrode_str, tetrode_status = line.split(' ')
                if int(tetrode_status) == 1:
                    tetrode_str.find('_')
                    tet_number = int(tetrode_str[tetrode_str.find('_') + 1:])
                    active_tetrode.append(tet_number)
    return active_tetrode
