code: def abort(self, err):
          
          if _debug: IOCB._debug("abort(%d) %r", self.ioID, err)
  
          if self.ioController:
              # pass to controller
              self.ioController.abort_io(self, err)
          elif self.ioState < COMPLETED:
              # just fill in the data
              self.ioState = ABORTED
              self.ioError = err
              self.trigger()
docs: Called by a client to abort a transaction.