code: public <T> Tuple<T> giveTuple(TypeTag tag) {
          realizeCacheFor(tag, emptyStack());
          return cache.getTuple(tag);
      }
docs: Returns a tuple of two different prefabricated values of the specified
  type.
  
  @param <T> The returned tuple will have this generic type.
  @param tag A description of the desired type, including generic
  parameters.
  @return A tuple of two different values of the given type.