pan class="s2">&quot;elements&quot;</span><span class="p">,</span> <span class="s2">&quot;positions&quot;</span><span class="p">]</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="nb">all</span><span class="p">([</span><span class="n">r</span> <span class="ow">in</span> <span class="bp">self</span> <span class="k">for</span> <span class="n">r</span> <span class="ow">in</span> <span class="n">required</span><span class="p">]):</span>
            <span class="k">raise</span> <s