pan> <span class="identifier">CategoryOrTraversal</span> <span class="special">=</span> <span class="identifier">use_default</span>
  <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Reference</span>           <span class="special">=</span> <span class="identifier">use_default</span>
  <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Difference</span> <span class="special">=</span> <span class="identifier">use_default</span>