If GO keys point to the same GOTerm, return new go2obj w/no duplicates.

def get_go2obj_unique(go2obj):
    """If GO keys point to the same GOTerm, return new go2obj w/no duplicates."""
    # Find the unique GO Terms that are represented for each GO in go2obj
    goid2gokeys = cx.defaultdict(set)
    for goid, goobj in go2obj.items():
        goid2gokeys[goobj.id].add(goid)
    go_unique = set()
    for goid, gos_seen in goid2gokeys.items():
        # Return main GO ID, if it is present in the go2obj keys
        if goid in gos_seen:
            go_unique.add(goid)
        # Otherwise return an alternate GO ID
        else:
            go_unique.add(next(iter(gos_seen)))
    return go_unique