class="p">:</span> <span class="nb">list</span><span class="p">,</span> <span class="n">required_columns</span><span class="p">:</span> <span class="nb">set</span><span class="p">,</span>
                       <span class="n">partitioner</span><span class="o">=</span><span class="n">PassThroughPartitioner</span><span class="p">(),</span> <span class="n">placement_strategy</span> <span class="o">=</span> <span class="n">CustomChannelsStrategy</span><span class="p">(</span><span class="mi">1</span><span clas