span><span class="n">first</span> <span class="o">=</span> <span
            class="n">first</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">last</span> <span class="o">=</span> <span
            class="n">last</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">weight</span> <span class="o">=</span> <span
            class="n">weight</span>  <span class="c1"># Sum of non tree edges adjacents to edge in tree # TODO: see self.replace()</span>
