pan> <span class="identifier">mapped_type</span><span class="special">&gt;</span></code>. In order to reproduce this interface in
      <span class="bold"><strong>Boost.Intrusive</strong></span> it shall require that objects
      stored in the intrusive containers contain that <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code> member
      with <code class="computeroutput"><span class="identifier">pair</span><span class