code: func (a *AdafruitMotorHatDriver) setAllPWM(conn Connection, on, off int32) (err error) {
  	// register and values to be written to that register
  	regVals := make(map[int][]byte)
  	regVals[0] = []byte{byte(_AllLedOnL), byte(on & 0xff)}
  	regVals[1] = []byte{byte(_AllLedOnH), byte(on >> 8)}
  	regVals[2] = []byte{byte(_AllLedOffL), byte(off & 0xFF)}
  	regVals[3] = []byte{byte(_AllLedOffH), byte(off >> 8)}
  	for i := 0; i < len(regVals); i++ {
  		if _, err = conn.Write(regVals[i]); err != nil {
  			return
  		}
  	}
  	return
  }
docs: // setAllPWM sets all PWM channels for the given address