/span> <span class="kc">None</span>
    <span class="n">iterators</span> <span class="o">=</span> <span class="p">[]</span>
    <span class="k">for</span> <span class="n">arg</span> <span class="ow">in</span> <span class="n">args</span><span class="p">:</span>
        <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">arg</span><span class="p">,</span> <span class="nb">tuple</span><span class="p">):</span>
            <span class="n">r</span><span class="p">,