code: public static <T> Transformer<T, List<T>> toListUntilChanged() {
          Func2<Collection<T>, T, Boolean> equal = HolderEquals.instance();
          return toListWhile(equal);
      }
docs: Returns a {@link Transformer} that returns an {@link Observable} that is
  a buffering of the source Observable into lists of sequential items that
  are equal.
  
  <p>
  For example, the stream
  {@code Observable.just(1, 1, 2, 2, 1).compose(toListUntilChanged())}
  would emit {@code [1,1], [2], [1]}.
  
  @param <T>
  the generic type of the source Observable
  @return transformer as above