code: def request(self, persist_id=None):
          
          node = new_ele("cancel-commit")
          if persist_id is not None:
              sub_ele(node, "persist-id").text = persist_id
  
          return self._request(node)
docs: Cancel an ongoing confirmed commit. Depends on the `:candidate` and `:confirmed-commit` capabilities.
  
          *persist-id* value must be equal to the value given in the <persist> parameter to the previous <commit> operation.