docs: protected void appendConstrainedExtends(
  			GenerationContext context,
  			JvmGenericType owner, Class<?> defaultJvmType,
  			Class<? extends XtendTypeDeclaration> defaultSarlType,
  			JvmParameterizedTypeReference supertype) {
  		final List<? extends JvmParameterizedTypeReference> supertypes;
  		if (supertype == null) {
  			supertypes = Collections.emptyList();
  		} else {
  			supertypes = Collections.singletonList(supertype);
  		}
  		appendConstrainedExtends(context, owner, defaultJvmType, defaultSarlType, supertypes);
  	}