pan> <span class="n">i</span><span class="p">,</span> <span class="n">periodic</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">pbc</span><span class="p">):</span>
                <span class="k">if</span> <span class="n">periodic</span><span class="p">:</span>
                    <span class="c1"># Yes, we need to do it twice.</span>
                    <span class="n">scaled_positions</span><span 