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