private Element getServicesFromReader(Reader reader) {
        Document doc = XmlHelper.getDocument(reader);
        return doc.getDocumentElement();
    }
Creates all the config models specified in the given XML element and
passes their respective XML node as parameter.

@param root The Root to set as parent for all plugins
@param servicesRoot XML root node of the services file
config-model/src/main/java/com/yahoo/config/model/ConfigModelRepo.java