PID tuning information

                axis                      : axis (uint8_t)
                desired                   : desired rate (degrees/s) (float)
                achieved                  : achieved rate (degrees/s) (float)
                FF                        : FF component (float)
                P                         : P component (float)
                I                         : I component (float)
                D                         : D component (float)

def pid_tuning_encode(self, axis, desired, achieved, FF, P, I, D):
                '''
                PID tuning information

                axis                      : axis (uint8_t)
                desired                   : desired rate (degrees/s) (float)
                achieved                  : achieved rate (degrees/s) (float)
                FF                        : FF component (float)
                P                         : P component (float)
                I                         : I component (float)
                D                         : D component (float)

                '''
                return MAVLink_pid_tuning_message(axis, desired, achieved, FF, P, I, D)