code: def fetch(self, is_dl_forced=False):
          
  
          # create the connection details for Flybase
          cxn = {
              'host': 'chado.flybase.org', 'database': 'flybase', 'port': 5432,
              'user': 'flybase', 'password': 'no password'}
  
          self.dataset.setFileAccessUrl(
              ''.join(('jdbc:postgresql://', cxn['host'], ':', str(cxn['port']),
                       '/', cxn['database'])), is_object_literal=True)
  
          # process the tables
          # self.fetch_from_pgdb(self.tables,cxn,100)  # for testing
          self.fetch_from_pgdb(self.tables, cxn, None, is_dl_forced)
  
          for query_map in self.resources:
              query_fh = open(os.path.join(
                  os.path.dirname(__file__), query_map['query']), 'r')
              query = query_fh.read()
              self.fetch_query_from_pgdb(
                  query_map['outfile'], query, None, cxn)
  
          # we want to fetch the features,
          # but just a subset to reduce the processing time
          # query = \
          #    "SELECT " \
          #    " feature_id, dbxref_id, organism_id, name, uniquename, " \
          #    " null as residues, seqlen, md5checksum, type_id, is_analysis," \
          #    " timeaccessioned, timelastmodified, is_obsolete " \
          #    "FROM feature WHERE is_analysis = false"
  
          self.fetch_query_from_pgdb(
              'feature', self.querys['feature'], None, cxn, None, is_dl_forced)
  
          self._get_human_models_file()
          self.get_files(False)
          self.dataset.set_version_by_num(self.version_num)
  
          return
docs: :return: