ot defined &quot;</span>
                <span class="s2">&quot;for this descriptor: </span><span class="si">{}</span><span class="s2">&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">zs</span><span class="o">.</span><span class="n">difference</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_atomic_number_set</span><span class="p">))</span>
            <span class="p">)</span></div>

<div class="viewco