Get namedtuples of GOEA results, split into BP, MF, CC.

def get_ns2nts(results, fldnames=None, **kws):
        """Get namedtuples of GOEA results, split into BP, MF, CC."""
        ns2nts = cx.defaultdict(list)
        nts = MgrNtGOEAs(results).get_goea_nts_all(fldnames, **kws)
        for ntgoea in nts:
            ns2nts[ntgoea.NS].append(ntgoea)
        return ns2nts