docs: public static ExtensionElement parseExtensionElement(String elementName, String namespace,
                      XmlPullParser parser, XmlEnvironment outerXmlEnvironment) throws XmlPullParserException, IOException, SmackParsingException {
          ParserUtils.assertAtStartTag(parser);
          // See if a provider is registered to handle the extension.
          ExtensionElementProvider<ExtensionElement> provider = ProviderManager.getExtensionProvider(elementName, namespace);
          if (provider != null) {
                  return provider.parse(parser, outerXmlEnvironment);
          }
  
          // No providers registered, so use a default extension.
          return StandardExtensionElementProvider.INSTANCE.parse(parser, outerXmlEnvironment);
      }