class="p">):</span>

            <span class="k">if</span> <span class="p">((</span><span class="n">site_j</span><span class="o">.</span><span class="n">index</span><span class="p">,</span> <span class="n">site_j</span><span class="o">.</span><span class="n">jimage</span><span class="p">)</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">seen_indices</span> <span class="ow">and</span>
                    <span class="p">(</span><span class="n">site_j</span><span class="o">.</span