code: def _process_diseases(self, limit=None):
          
  
          LOG.info("Processing diseases")
          if self.test_mode:
              graph = self.testgraph
          else:
              graph = self.graph
          line_counter = 0
          model = Model(graph)
          raw = '/'.join((self.rawdir, self.files['disease']['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
                  (disease_id, disease_name) = row
  
                  disease_id = 'KEGG-'+disease_id.strip()
                  if disease_id not in self.label_hash:
                      self.label_hash[disease_id] = disease_name
  
                  if self.test_mode and disease_id not in self.test_ids['disease']:
                      continue
  
                  # Add the disease as a class.
                  # we don't get all of these from MONDO yet see:
                  # https://github.com/monarch-initiative/human-disease-ontology/issues/3
                  model.addClassToGraph(disease_id, disease_name)
                  # not typing the diseases as DOID:4 yet because
                  # I don't want to bulk up the graph unnecessarily
  
                  if not self.test_mode and (
                          limit is not None and line_counter > limit):
                      break
  
          LOG.info("Done with diseases")
          return
docs: This method processes the KEGG disease IDs.
  
          Triples created:
          <disease_id> is a class
          <disease_id> rdfs:label <disease_name>
          :param limit:
          :return: