lways holds:
          </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
                <code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_generator</span><span class="special">&lt;</span><span class="identifier">G</span><span class="special">::</span><span class="identifier">subject_type</span><span class="special">&gt;::</span><span class="identifier">type</span></code> e