code: public T fromXML(String xml) throws Exception {
      Unmarshaller u = this.getUnmarshaller();
      u.setProperty(MarshallerProperties.MEDIA_TYPE, "application/xml");
      T result = this.fromString(u, xml);
      return result;
    }
docs: get an instance of T for the given xml string
  
  @param xml
  - the xml representation of the <T> instance
  @return T
  @throws Exception
  - if the conversion fails