code: def get_grp2code2nt(self):
          
          grp2code2nt = cx.OrderedDict([(g, []) for g in self.grps])
          for code, ntd in self.code2nt.items():
              grp2code2nt[ntd.group].append((code, ntd))
          for grp, nts in grp2code2nt.items():
              grp2code2nt[grp] = cx.OrderedDict(nts)
          return grp2code2nt
docs: Return ordered dict for group to namedtuple