CoffeeConfigurationForm form error

I just tried to install your module on d8 and got the following error see attached image for more information.

Fatal error: Class Drupal\coffee\Form\CoffeeConfigurationForm contains 1 abstract method and must therefore be declared abstract or implement the remaining methods

I implemented the extra method in the CoffeeConfigurationForm class see patch

protected function getEditableConfigNames() {
		
 }