def tuplify(df, name):
    """Pads a heirarchical column name with enough empty strings to be used as
    a column specification for a heirarchical DataFrame. For example:
        tuplify(df, ('roi_atoms', 'Fz')) = ('roi_atoms', 'Fz', '', '')
    """
    m = df.columns.nlevels
    if type(name) != tuple:
        name = (name,)
    while len(name) < m:
        name += ('',)
    return name