implifying
        the task of writing a new storage policy.
      </p>
<p>
        This class may implement a function <code class="computeroutput"><span class="identifier">destroy</span><span class="special">()</span></code> being called during destruction of the
        last copy of a <code class="computeroutput"><span class="identifier">multi_pass</span></code>.
        This function should be used to free any of the shared data items the policy
        might have allocated during construction of its <c