code: public Content getSerializableMethods(String heading, Content serializableMethodContent) {
          Content headingContent = new StringContent(heading);
          Content serialHeading = HtmlTree.HEADING(HtmlConstants.SERIALIZED_MEMBER_HEADING,
                  headingContent);
          Content li = HtmlTree.LI(HtmlStyle.blockList, serialHeading);
          li.addContent(serializableMethodContent);
          return li;
      }
docs: Add serializable methods.
  
  @param heading the heading for the section
  @param serializableMethodContent the tree to be added to the serializable methods
  content tree
  @return a content tree for the serializable methods content