Get geneid2nt given a list of namedtuples.

def _get_geneid2nt(nts):
        """Get geneid2nt given a list of namedtuples."""
        geneid2nt = {}
        for ntd in nts:
            geneid = ntd.GeneID
            if geneid not in geneid2nt:
                geneid2nt[geneid] = ntd
            else:
                print("DUPLICATE GeneID FOUND {N:9} {SYM}".format(N=geneid, SYM=ntd.Symbol))
        return geneid2nt