code: private void loadEngines() {
          try {
              ClassLoader cl = ModelExtractors.class.getClassLoader();
              Enumeration<URL> resources = cl.getResources(PROPERTIES);
              while (resources.hasMoreElements()) {
                  URL url = resources.nextElement();
                  Properties props = new Properties();
                  props.load(url.openStream());
                  for (Map.Entry<Object, Object> entry : props.entrySet()) {
                      String className = (String) entry.getKey();
                      String[] extensions = ((String) entry.getValue()).split(",");
                      loadAndRegisterEngine(className, extensions);
                  }
              }
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
docs: This method is used internally to load markup engines. Markup engines are found using descriptor files on
  classpath, so adding an engine is as easy as adding a jar on classpath with the descriptor file included.