code: @Override
      public void addContent(CharSequence stringContent) {
          if (!content.isEmpty()) {
              Content lastContent = content.get(content.size() - 1);
              if (lastContent instanceof StringContent)
                  lastContent.addContent(stringContent);
              else
                  addContent(new StringContent(stringContent));
          }
          else
              addContent(new StringContent(stringContent));
      }
docs: This method adds a string content to the htmltree. If the last content member
  added is a StringContent, append the string to that StringContent or else
  create a new StringContent and add it to the html tree.
  
  @param stringContent string content that needs to be added