code: def _get_name(self, graph, group=None):
          
          if group is not None:
              graph = graph.get_subgraph(group, normalize=True)
  
          fingerprint = graph.fingerprint.tobytes()
          name = self.name_cache.get(fingerprint)
          if name is None:
              name = "NM%02i" % len(self.name_cache)
              self.name_cache[fingerprint] = name
          return name
docs: Convert a molecular graph into a unique name
  
             This method is not sensitive to the order of the atoms in the graph.