TypeError Traceback (most recent call last)

<ipython-input-39-68d249d7c772> in <module>
1 #加载数据执行策略回测，并计算相关统计指标，绘制结果图表
2 engine.load_data()
----> 3 engine.run_backtesting()
4 df = engine.calculate_result()
5 engine.calculate_statistics()

d:\work\vnstudio\lib\site-packages\vnpy\app\spread_trading\backtesting.py in run_backtesting(self)
168
169 self.datetime = data.datetime
--> 170 self.callback(data)
171
172 self.strategy.inited = True

TypeError: 'NoneType' object is not callable

请问这里callback是需要如何配置？