code: public Reader createReaderForXMLFile(String pluginKey) {
      ClassLoader classLoader = contributingPluginKeyToClassLoader.get(pluginKey);
      String xmlFilePath = getXMLFilePath(pluginKey);
      return new InputStreamReader(classLoader.getResourceAsStream(xmlFilePath), StandardCharsets.UTF_8);
    }
docs: Creates a new {@link java.io.Reader} for the XML file that contains the model contributed by the given plugin.
  
  @param pluginKey the key of the plugin that contributes the XML file
  @return the reader, that must be closed once its use is finished.