"programlisting"><span class="identifier">element</span> <span class="identifier">containers</span><span class="special">:</span>     <span class="identifier">interval</span> <span class="identifier">containers</span><span class="special">:</span>
<span class="special">&amp;=</span> <span class="special">|</span> <span class="identifier">e</span> <span class="identifier">b</span> <span class="identifier">s</span> <span class="identifier">m</span>            <span class="special">&amp;=</span> <span class="s