code: private void addWrapper(MethodSpec.Builder method, String pattern) {
      method.addComment("$S", pattern);
      for (Node node : WRAPPER_PARSER.parseWrapper(pattern)) {
        if (node instanceof Text) {
          method.addStatement("b.append($S)", ((Text)node).text());
  
        } else if (node instanceof Field) {
          Field field = (Field)node;
          switch (field.ch()) {
            case '0':
              method.beginControlFlow("if (timeType != null)");
              method.addStatement("formatTime(timeType, d, b)");
              method.nextControlFlow("else");
              method.addStatement("formatSkeleton(timeSkel, d, b)");
              method.endControlFlow();
              break;
  
            case '1':
              method.beginControlFlow("if (dateType != null)");
              method.addStatement("formatDate(dateType, d, b)");
              method.nextControlFlow("else");
              method.addStatement("formatSkeleton(dateSkel, d, b)");
              method.endControlFlow();
              break;
          }
        }
      }
    }
docs: Formats a date-time combination into a wrapper format, e.g. "{1} at {0}"