/span>
        <span class="k">if</span> <span class="n">delta</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">delta</span> <span class="o">=</span> <span class="mi">1</span>
        <span class="k">else</span><span class="p">:</span> 
            <span class="bp">self</span><span class="o">.</span><span class="n">delta</span> <span class="o">=</span> <span class="n">delta</span> 

        