> <span class="o">==</span> <span class="kc">False</span><span class="p">:</span>
            <span class="k">if</span> <span class="n">root</span> <span class="o">==</span> <span class="kc">None</span><span class="p">:</span>
                <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s2">&quot;You must specify a root for the tree.&quot;</span><span class="p">)</span>
            <span class="k">else</span><span class="p">:</span>
                <spa