code: def clear_transaction(self):
          
          with self._transaction_lock:
              local = self._transaction_local
              if not local.pipes:
                  raise ValueError('No transaction is currently active.')
              local.abort()
docs: Clear the currently active transaction (if exists). If the
          transaction stack is not empty, then a new pipeline will
          be initialized.
  
          :returns: No return value.
          :raises: ``ValueError`` if no transaction is active.