code: public <T> void realizeCacheFor(TypeTag tag, LinkedHashSet<TypeTag> typeStack) {
          if (!cache.contains(tag)) {
              Tuple<T> tuple = createTuple(tag, typeStack);
              addToCache(tag, tuple);
          }
      }
docs: Makes sure that values for the specified type are present in the cache,
  but doesn't return them.
  
  @param <T> The desired type.
  @param tag A description of the desired type, including generic
  parameters.
  @param typeStack Keeps track of recursion in the type.