n</span><span class="p">],</span> <span class="n">atom</span>
        <span class="p">)</span>

    <span class="c1"># go through all pairs</span>
    <span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="p">(</span><span class="n">idx</span><span class="p">,</span> <span class="n">r</span><span class="p">)</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">pairs</span><span class="o">.</span><span class="n">iterrows<