Get the GO ID with the lowest descendants count.

def get_most_specific_dcnt(goids, go2nt):
    """Get the GO ID with the lowest descendants count."""
    # go2nt_usr = {go:go2nt[go] for go in goids}
    # return min(go2nt_usr.items(), key=lambda t: t[1].dcnt)[0]
    return min(_get_go2nt(goids, go2nt), key=lambda t: t[1].dcnt)[0]