code: public ToStringBuilder appendSuper(final String superToString) {
          if (superToString != null) {
              style.appendSuper(buffer, superToString);
          }
          return this;
      }
docs: <p>Append the <code>toString</code> from the superclass.</p>
  
  <p>This method assumes that the superclass uses the same <code>ToStringStyle</code>
  as this one.</p>
  
  <p>If <code>superToString</code> is <code>null</code>, no change is made.</p>
  
  @param superToString  the result of <code>super.toString()</code>
  @return this
  @since 2.0