code: def run_start_backup(cls):
          
          def handler(popen):
              assert popen.returncode != 0
              raise UserException('Could not start hot backup')
  
          # The difficulty of getting a timezone-stamped, UTC,
          # ISO-formatted datetime is downright embarrassing.
          #
          # See http://bugs.python.org/issue5094
          label = 'freeze_start_' + (datetime.datetime.utcnow()
                                     .replace(tzinfo=UTC()).isoformat())
  
          return cls._dict_transform(psql_csv_run(
                  "SELECT file_name, "
                  "  lpad(file_offset::text, 8, '0') AS file_offset "
                  "FROM pg_{0}file_name_offset("
                  "  pg_start_backup('{1}'))".format(cls._wal_name(), label),
                  error_handler=handler))
docs: Connects to a server and attempts to start a hot backup
  
          Yields the WAL information in a dictionary for bookkeeping and
          recording.