code: def _process(self, on_commit: UpdateCallable, on_rollback: UpdateCallable) -> Any:
          
  
          _debug("---> commiting", on_commit)
          result = self._do_with_retry(on_commit)
  
          if len(self._transactions) > 0:
              # add statement to rollback log in case something goes wrong
              self._transactions[-1].insert(0, on_rollback)
  
          return result
docs: Process action. oncommit is a callback to execute action, onrollback is
          a callback to execute if the oncommit() has been called and a rollback
          is required