span class="identifier">value_type</span></code>
        in your implementation file:
      </p>
<p>
        In this header file we define a class (<code class="computeroutput"><span class="identifier">MyClassHolder</span><span class="special">)</span></code> that holds a <code class="computeroutput"><span class="identifier">vector</span></code>
        of an incomplete type (<code class="computeroutput"><span class="identifier">MyClass</span></code>)
        that it's only forward declared.
      </p>
<p>
