docs: public static synchronized List<Class< ? >> locateAll(final String serviceName) {
          if ( serviceName == null ) {
              throw new IllegalArgumentException( "serviceName cannot be null" );
          }
          List<Class< ? >> classes = new ArrayList<Class< ? >>();
          if ( factories != null ) {
              List<Callable<Class< ? >>> l = factories.get( serviceName );
              if ( l != null ) {
                  for ( Callable<Class< ? >> c : l ) {
                      try {
                          classes.add( c.call() );
                      } catch ( Exception e ) {
                      }
                  }
              }
          }
          return classes;
      }