    &#39;&#39;&#39;</span>
    <span class="n">variable</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">variable_key</span><span class="p">,</span> <span class="n">default</span><span class="p">)</span>
    <span class="k">if</span> <span class="n">variable</span> <span class="ow">is</span> <span class="kc">None</span> <span class="ow">and</span> <span clas