an class="o">.</span><span class="n">props</span><span class="p">[</span><span class="s1">&#39;FrameNumber&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="n">n</span>
   <span class="k">return</span> <span class="n">fout</span>
<span class="o">...</span>
<span class="n">ModifyFrame</span><span class="p">(</span><span class="n">clip</span><span class="o">=</span><span class="n">clip</span><span class="p">,</span> <span class="n">clips</span><span class="o">=</span><span class="n">cl