code: def _process_genes_kegg2ncbi(self, limit=None):
          
  
          LOG.info("Processing KEGG gene IDs to NCBI gene IDs")
          if self.test_mode:
              graph = self.testgraph
          else:
              graph = self.graph
          model = Model(graph)
          line_counter = 0
  
          raw = '/'.join((self.rawdir, self.files['ncbi']['file']))
          with open(raw, 'r', encoding="iso-8859-1") as csvfile:
              filereader = csv.reader(csvfile, delimiter='\t', quotechar='\"')
              for row in filereader:
                  line_counter += 1
                  (kegg_gene_id, ncbi_gene_id, link_type) = row
  
                  if self.test_mode and kegg_gene_id not in self.test_ids['genes']:
                      continue
  
                  # Adjust the NCBI gene ID prefix.
                  ncbi_gene_id = re.sub(r'ncbi-geneid', 'NCBIGene', ncbi_gene_id)
                  kegg_gene_id = 'KEGG-' + kegg_gene_id
  
                  # Adding the KEGG gene ID to the graph here is redundant,
                  # unless there happens to be additional gene IDs in this table
                  # not present in the genes table.
                  model.addClassToGraph(kegg_gene_id, None)
                  model.addClassToGraph(ncbi_gene_id, None)
                  model.addEquivalentClass(kegg_gene_id, ncbi_gene_id)
  
                  if not self.test_mode and (
                          limit is not None and line_counter > limit):
                      break
  
          LOG.info("Done with KEGG gene IDs to NCBI gene IDs")
          return
docs: This method maps the KEGG human gene IDs
              to the corresponding NCBI Gene IDs.
  
          Triples created:
          <kegg_gene_id> is a class
          <ncbi_gene_id> is a class
          <kegg_gene_id> equivalentClass <ncbi_gene_id>
          :param limit:
          :return: