code: def equivalent_vertices(self):
          
          level1 = {}
          for i, row in enumerate(self.vertex_fingerprints):
              key = row.tobytes()
              l = level1.get(key)
              if l is None:
                  l = set([i])
                  level1[key] = l
              else:
                  l.add(i)
          level2 = {}
          for key, vertices in level1.items():
              for vertex in vertices:
                  level2[vertex] = vertices
          return level2
docs: A dictionary with symmetrically equivalent vertices.