docs: public void printString(Color color, final PrintWriter writer) {
          color._switch(new ColorSwitchBlock() {            
              @Override
              public void _case(Red x) {
                  writer.print("red");
              }
              
              @Override
              public void _case(Green x) {
                  writer.print("green");                
              }
              
              @Override
              public void _case(Blue x) {
                  writer.print("blue");
              }           
          });
      }