}

  private TypeToken<? super T> getSupertypeFromUpperBounds(
      Class<? super T> supertype, Type[] upperBounds) {
    for (Type upperBound : upperBounds) {
      @SuppressWarnings("unchecked") // T's upperbound is <? super T>.
      TypeToken<? super T> bound = (TypeToken<? super T>) of(upperBound);
      if (bound.isSubtypeOf(supertype)) {
        @SuppressWarnings({"rawtypes", "unchecked"}) // guarded by the isSubtypeOf check.