code: @Nonnull
    public static ToStringGenerator getDerived (@Nonnull final String sSuperToString)
    {
      // We don't need the object if "super.toString" is involved, because in
      // super.toString the object is already emitted!
      return new ToStringGenerator (null)._appendSuper (sSuperToString);
    }
docs: Create a {@link ToStringGenerator} for derived classes where the base class
  also uses the {@link ToStringGenerator}. This avoids that the implementing
  class name is emitted more than once.
  
  @param sSuperToString
  Always pass in <code>super.toString ()</code>
  @return Never <code>null</code>