an class="bp">self</span><span
            class="p">,</span> <span class="n">where</span><span class="p">,</span> <span class="n">data</span><span
            class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">priority</span><span
            class="o">=</span><span class="kc">None</span><span class="p">):</span>
        <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        (TODO) different balance : just from the children to the root</span>
<span class="sd