  <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">ring</span><span class="p">)</span> <span class="o">==</span> <span class="mi">3</span> <span class="ow">and</span> <span class="n">ring_spec</span> <span class="ow">in</span> <span class="p">[[</span><span class="s2">&quot;C&quot;</span><span class="p">,</span> <span class="s2">&quot;C&quot;</span><span class="p">,</span> <span class="s2">&quot;O&quot;</span><span class="p">],</span>
                             