code: def _trade(self, event):
          "内部函数"
          print('==================================market enging: trade')
          print(self.order_handler.order_queue.pending)
          print('==================================')
          self.order_handler._trade()
          print('done'f _trade(self, event):
          "内部函数"
          print('==================================market enging: trade')
          print(self.order_handler.order_queue.pending)
          print('==================================')
          self.order_handler._trade()
          print('done')
docs: 内部函数