)</span> <span class="k">throws</span> <span class="o">-&gt;</span> <span class="kt">Void</span><span class="p">)?</span> <span class="o">=</span> <span class="kc">nil</span><span class="p">,</span> <span class="nv">afterNext</span><span class="p">:</span> <span class="p">((</span><span class="kt">Element</span><span class="p">)</span> <span class="k">throws</span> <span class="o">-&gt;</span> <span class="kt">Void</span><span class="p">)?</span> <span class="o">=</span> <span class="kc">nil</span><span cla