docs: def update_todo_item(self, item_id, content, party_id=None, notify=False):
          """
          Modifies an existing item. The values work much like the "create item"
          operation, so you should refer to that for a more detailed explanation.
          """
          path = '/todos/update_item/%u' % item_id
          req = ET.Element('request')
          item = ET.Element('request')
          ET.SubElement(item, 'content').text = str(content)
          if party_id is not None:
              ET.SubElement(req, 'responsible-party').text = str(party_id)
              ET.SubElement(req, 'notify').text = str(bool(notify)).lower()
          return self._request(path, req)