code: func (d *TSL2561Driver) SetGain(gain TSL2561Gain) error {
  	if err := d.enable(); err != nil {
  		return err
  	}
  
  	timeGainVal := uint8(d.integrationTime) | uint8(gain)
  	if err := d.connection.WriteByteData(tsl2561CommandBit|tsl2561RegisterTiming, timeGainVal); err != nil {
  		return err
  	}
  	d.gain = gain
  
  	return d.disable()
  }
docs: // SetGain adjusts the TSL2561 gain (sensitivity to light)