pan><span class="p">,</span>
                <span class="n">Q_a</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">Q_b</span><span class="p">,</span>
                <span class="n">Q_b</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">Q_a</span><span class="p">,</span>
            <span class="p">)</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">Q</span> <span class="o">=</span