o">.</span><span class="n">b</span> <span class="o">=</span> <span class="n">b</span> <span class="ow">or</span> <span class="bp">self</span><span class="o">.</span><span class="n">_B</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">tau</span> <span class="o">=</span> <span class="n">tau</span> <span class="ow">or</span> <span class="bp">self</span><span class="o">.</span><span class="n">_TAU</span>

        <span class="bp">self</span><span class="o">.</span><span class="n