code: public static void exportChildOrderProperty(JsonWriter writer, Resource resource)
              throws IOException {
          List<String> names = new ArrayList<>();
          Iterable<Resource> children = resource.getChildren();
          for (Resource child : children) {
              String name = child.getName();
              if (!ResourceUtil.CONTENT_NODE.equals(name)) {
                  names.add(name);
              }
          }
          if (names.size() > 0) {
              writer.name(MappingRules.CHILD_ORDER_NAME);
              writer.beginArray();
              for (String name : names) {
                  if (!ResourceUtil.CONTENT_NODE.equals(name)) {
                      writer.value(name);
                  }
              }
              writer.endArray();
          }
      }
docs: Writes the names of all children (except the 'jcr:content' child) into one array value
  named '_child_order_' as a hint to recalculate the original order of the children.
  
  @param writer
  @param resource
  @throws IOException