code: public static <T> T release(final Resource<T> resource, final T instance) {
      return holder.releaseInternal(resource, instance);
    }
docs: Releases an instance of the given resource.
  
  <p>The instance must have been obtained from {@link #get(Resource)}. Otherwise will throw
  IllegalArgumentException.
  
  <p>Caller must not release a reference more than once. It's advisory that you clear the
  reference to the instance with the null returned by this method.
  
  @param resource the singleton Resource object that identifies the released static resource
  @param instance the released static resource
  
  @return a null which the caller can use to clear the reference to that instance.