def separate_ccds(cubes: list) -> tuple:
    """Return a tuple of six values, either HiColorCubes, or None."""
    red4 = red5 = ir10 = ir11 = bg12 = bg13 = None
    for c in cubes:
        if c.ccdnumber == "4":
            red4 = c
        elif c.ccdnumber == "5":
            red5 = c
        elif c.ccdnumber == "10":
            ir10 = c
        elif c.ccdnumber == "11":
            ir11 = c
        elif c.ccdnumber == "12":
            bg12 = c
        elif c.ccdnumber == "13":
            bg13 = c
        else:
            # Not one of the six that we care about,
            # so we'll silently ignore it.
            pass
    return red4, red5, ir10, ir11, bg12, bg13