code: func WithTSL2561Gain1X(c Config) {
  	d, ok := c.(*TSL2561Driver)
  	if ok {
  		d.gain = TSL2561Gain1X
  		return
  	}
  	// TODO: return errors.New("Trying to set Gain for non-TSL2561Driver")
  }
docs: // WithTSL2561Gain1X option sets the TSL2561Driver gain to 1X