of lower edges of the vertex v.</span>

<span class="sd">        &quot;&quot;&quot;</span>
        <span class="n">L</span> <span class="o">=</span> <span class="p">[</span><span class="n">n</span> <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">neighbors</span><span class="p">(</span><span class="n">v</span><span class="p">)]</span>
        <span class="n">gv</span> <span class="o">=</span> <span class="n">np