code: func (s *SSD1306Driver) SetContrast(contrast byte) (err error) {
  	if contrast < 0 || contrast > 255 {
  		return fmt.Errorf("contrast value must be between 0-255")
  	}
  	if err = s.command(ssd1306SetContrast); err != nil {
  		return err
  	}
  	return s.command(contrast)
  }
docs: // SetContrast sets the display contrast (0-255).