span><span class="n">t</span><span class="o">.</span><span class="n">inflow_dict</span><span class="p">)</span> <span class="o">|</span>
             <span class="nb">set</span><span class="p">(</span><span class="n">t</span><span class="o">.</span><span class="n">outflow_dict</span><span class="p">))</span> <span class="o">-</span> <span class="nb">set</span><span class="p">([</span><span class="n">m</span><span class="o">.</span><span class="n">id</span> <span class="k">for</span> <span class="n">m</span>