docs: def create_todo_item(self, list_id, content, party_id=None, notify=False):
          """
          This call lets you add an item to an existing list. The item is added
          to the bottom of the list. If a person is responsible for the item,
          give their id as the party_id value. If a company is responsible,
          prefix their company id with a 'c' and use that as the party_id value.
          If the item has a person as the responsible party, you can use the
          notify key to indicate whether an email should be sent to that person
          to tell them about the assignment.
          """
          path = '/todos/create_item/%u' % list_id
          req = ET.Element('request')
          ET.SubElement(req, '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)