     and <code class="computeroutput"><span class="identifier">shared</span></code>. The <code class="computeroutput"><span class="identifier">unique</span></code> class needs to implement all required
        functions for a particular policy type. In addition it may hold all member
        data items being <span class="emphasis"><em>unique</em></span> for a particular instance of
        a <code class="computeroutput"><span class="identifier">multi_pass</span></code> (hence the name).
        The <code cl