def read_radial_filterwheel(fname):
    """Read radially variable filterwheel transmissions.

    Parameters
    ----------
    fname : str


    Returns
    -------
    dict of list
        Dictionary where keys are filter names and values are lists. Each
        item in the list is a two-tuple giving the radius and filter function
        (in the form of a SampledFunction).
    """
    result = {}
    with open(fname, 'r') as f:
        for line in f:
            band, _, bandfname = line.split()
            if band not in result:
                result[band] = []
            result[band].append(bandfname)
    return result
