code: public RedGBuilder<T> withDummyFactory(final DummyFactory dummyFactory) {
          if (instance == null) {
              throw new IllegalStateException("Using the builder after build() was called is not allowed!");
          }
          instance.setDummyFactory(dummyFactory);
          return this;
      }
docs: Sets the dummy factory
  @param dummyFactory The dummy factory
  @return The builder itself
  @see AbstractRedG#setDummyFactory(DummyFactory)