code: def uncomplete(self):
          
          args = {
              'project_id': self.project.id,
              'ids': [self.id]
          }
          owner = self.project.owner
          _perform_command(owner, 'item_uncomplete', args)
docs: Mark the task uncomplete.
  
          >>> from pytodoist import todoist
          >>> user = todoist.login('john.doe@gmail.com', 'password')
          >>> project = user.get_project('PyTodoist')
          >>> task = project.add_task('Install PyTodoist')
          >>> task.uncomplete()