Separate alt GO IDs and key GO IDs.

def get_goobjs_altgo2goobj(go2obj):
    """Separate alt GO IDs and key GO IDs."""
    goobjs = set()
    altgo2goobj = {}
    for goid, goobj in go2obj.items():
        goobjs.add(goobj)
        if goid != goobj.id:
            altgo2goobj[goid] = goobj
    return goobjs, altgo2goobj