"bold"><strong>Semantics</strong></span>: Returns a sequence containing
            the elements of <code class="computeroutput"><span class="identifier">Sequence</span></code>
            for which <code class="computeroutput"><span class="identifier">Pred</span></code> evaluates
            to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>.
      