code: public Object fragment(Map model, String templateText) throws IOException, ClassNotFoundException {
          Template template = cachedFragments.get(templateText);
          if (template==null) {
              template = engine.createTemplate(new StringReader(templateText));
              cachedFragments.put(templateText, template);
          }
          template.make(model).writeTo(out);
          return this;
      }
docs: Renders an embedded template as a fragment. Fragments are cached in a template, meaning that
  if you use the same fragment in a template, it will only be compiled once, but once <b>per template
  instance</b>. This is less performant than using {@link #layout(java.util.Map, String)}.
  
  @param model model to be passed to the template
  @param templateText template body
  @return this template instance
  @throws IOException
  @throws ClassNotFoundException