<span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">expressions</span><span class="special">::</span><span class="identifier">attribute_keyword</span><span class="special">&lt;</span> <span class="identifier">DescriptorT</span><span class="special">,</span> <span class="identifier">ActorT</span> <span class="special">&gt;</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">,</span> <span class="identifier">Descript