span class="mi">10</span>
                <span class="n">y_pos</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span>

            <span class="n">E</span><span class="o">.</span><span class="n">append</span><span class="p">(((</span><span
            class="n">x_parent</span><span class="p">,</span> <span class="n">y_parent</span><span
            class="p">),</span> <span class="p">(</span><span class="n">x_pos</span><span class="p">,</span> <span
            class="n">y_pos</s