问当我用Python向我的调制解调器发送串行端口消息时，整数返回值意味着什么？

EN

    def write(self, data):
        """Output the given string over the serial port."""
        if not self.is_open:
            raise PortNotOpenError()
        #~ if not isinstance(data, (bytes, bytearray)):
            #~ raise TypeError('expected %s or bytearray, got %s' % (bytes, type(data)))
        try:
            # must call overloaded method with byte array argument
            # as this is the only one not applying encodings
            self._port_handle.Write(as_byte_array(data), 0, len(data))
        except System.TimeoutException:
            raise SerialTimeoutException('Write timeout')
        return len(data)