code: @SuppressWarnings("unchecked")
    public static <T> T fromXml(Class<T> clazz, String xml) {
      T object = (T) CLASS_2_XSTREAM_INSTANCE.get(clazz).fromXML(xml);
      return object;
    }
docs: xml -> pojo
  
  @param clazz
  @param xml
  @return