on should be used to free any of the shared data items the policy
        might have allocated during construction of its <code class="computeroutput"><span class="identifier">shared</span></code>
        part. Because of the way <code class="computeroutput"><span class="identifier">multi_pass</span></code>
        is implemented any allocated data members in <code class="computeroutput"><span class="identifier">shared</span></code>
        should <span class="underline">not</span> be deep copied in a copy
