code: def on(self):
          
          isOK = True
          try:
              if self.channelR!=None:
                  sub.call(["gpio", "-g", "mode", "{}".format(self.channelR), self.PIN_MODE_AUDIO ])
          except:
              isOK = False
              print("Open audio right channel failed.")
  
          try:
              if self.channelL!=None:
                  sub.call(["gpio","-g","mode", "{}".format(self.channelL), self.PIN_MODE_AUDIO ])
          except:
              isOK = False
              print("Open audio left channel failed.")
  
          return isOK
docs: !
          \~english
          Open Audio output. set pin mode to ALT0
          @return a boolean value. if True means open audio output is OK otherwise failed to open.
  
          \~chinese
          打开音频输出。 将引脚模式设置为ALT0
          @return 布尔值。 如果 True 表示打开音频输出成功，否则不成功。