pan><span class="p">:</span> <span class="n">neighbours</span><span class="p">(</span><span class="n">i</span><span class="p">)</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span>
                       <span class="nb">range</span><span class="p">(</span><span class="n">bonded_structure</span><span class="o">.</span><span class="n">structure</span><span class="o">.</span><span class="n">num_sites</span><span class="p">)}</span>

    <span class="n">seen_vertices</span> <sp