code: def compare_to_xrefs(self, xg1, xg2):
          
          ont = self.merged_ontology
          for (i,j,d) in xg1.edges(data=True):
              ont_left = self._id_to_ontology(i)
              ont_right = self._id_to_ontology(j)
              unique_lr = True
              num_xrefs_left = 0
              same_left = False
              if i in xg2:
                  for j2 in xg2.neighbors(i):
                      ont_right2 = self._id_to_ontology(j2)
                      if ont_right2 == ont_right:
                          unique_lr = False
                          num_xrefs_left += 1
                          if j2 == j:
                              same_left = True
              unique_rl = True
              num_xrefs_right = 0
              same_right = False
              if j in xg2:
                  for i2 in xg2.neighbors(j):
                      ont_left2 = self._id_to_ontology(i2)
                      if ont_left2 == ont_left:
                          unique_rl = False
                          num_xrefs_right += 1
                          if i2 == i:
                              same_right = True
  
              (x,y) = d['idpair']
              xg1[x][y]['left_novel'] = num_xrefs_left==0
              xg1[x][y]['right_novel'] = num_xrefs_right==0
              xg1[x][y]['left_consistent'] = same_left
              xg1[x][y]['right_consistent'] = same_right
docs: Compares a base xref graph with another one