an><span class="p">()[</span><span class="n">centers</span><span class="p">]</span>

        <span class="k">for</span> <span class="n">index</span><span class="p">,</span> <span class="n">i_atom</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">indices</span><span class="p">):</span>
            <span class="k">for</span> <span class="n">i_center</span><span class="p">,</span> <span class="n">center</span> <span class="ow">in</span> <span class="nb">