</code>
            to it's subject, if extracting <code class="computeroutput"><span class="identifier">T</span></code>
            from it's consumed attribute determined at generation-time to be valid.
            <a class="link" href="../../../advanced/customize/attribute_as.html" title="Atomically Extract an Attribute Value from a Container (Karma)"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">valid_as</span><span class="spec