code: public Content getSerializableFields(String heading, Content serializableFieldsTree) {
          HtmlTree li = new HtmlTree(HtmlTag.LI);
          li.addStyle(HtmlStyle.blockList);
          if (serializableFieldsTree.isValid()) {
              Content headingContent = new StringContent(heading);
              Content serialHeading = HtmlTree.HEADING(HtmlConstants.SERIALIZED_MEMBER_HEADING,
                      headingContent);
              li.addContent(serialHeading);
              li.addContent(serializableFieldsTree);
          }
          return li;
      }
docs: Add serializable fields.
  
  @param heading the heading for the section
  @param serializableFieldsTree the tree to be added to the serializable fileds
  content tree
  @return a content tree for the serializable fields content