span> <span class="identifier">extract</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">sys</span><span class="special">.</span><span class="identifier">attr</span><span class="special">(</span><span class="string">"version"</span><span class="special">));</span>
  <span class="identifier">std</span><span class="special">::</span><span class="identifier">co