an><span class="identifier">python</span><span class="special">::</span><span class="identifier">call</span><span class="special">&lt;</span><span class="keyword">void</span><span class="special">&gt;(</span><span class="identifier">callable</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
<span class="special">}</span>
</p