code: public static URL getResource(Class<?> contextClass, String resourceName) {
      URL url = contextClass.getResource(resourceName);
      checkArgument(
          url != null, "resource %s relative to %s not found.", resourceName, contextClass.getName());
      return url;
    }
docs: Given a {@code resourceName} that is relative to {@code contextClass}, returns a {@code URL}
  pointing to the named resource.
  
  @throws IllegalArgumentException if the resource is not found