code: def __get_genestr(self, itemid):
          
          if self.id2symbol is not None:
              symbol = self.id2symbol.get(itemid, None)
              if symbol is not None:
                  return symbol
          if isinstance(itemid, int):
              return str(itemid)
          return itemid
docs: Given a geneid, return the string geneid or a gene symbol.