/span><span class="n">add_node</span><span class="p">(</span><span class="s1">&#39;A&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
    <span class="n">graph</span><span class="o">.</span><span class="n">add_node</span><span class="p">(</span><span class="s1">&#39;B&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">)</span>
    <span class="n">