code: public String process(String filename, String source, Config conf) throws Exception {
      return process(filename, source, conf, getClass().getClassLoader());
    }
docs: Method that processes the provided source and returns the processed contents.
  
  @param filename name of the file
  @param source   contents of the file
  @param conf     application configuration
  @return the processed file contents
  @throws Exception if any error occurred