def get_triplet_from_mag(ch_name):
    """Get the triplet (one mag, two grads) from mag by name hacking.

    Parameters
    ----------
    ch_name : str
        Name of mag channel, e.g 'MEG 1231'.

    Returns
    -------
    list
        List of three channels, e.g ['MEG 1231', 'MEG 1232', 'MEG 1233']
    """ 
    return [ch_name, ch_name[:-1] + '2', ch_name[:-1] + '3']