an class="p">,</span>
    <span class="nv">header</span><span class="p">:</span> <span class="kt">Downstream</span><span class="o">.</span><span class="kt">Header</span><span class="p">?,</span>
    <span class="nv">completion</span><span class="p">:</span> <span class="p">((</span><span class="kt">StreamDataState</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="kt">Void</span><span class="p">)?</span>
<span class="p">)</span> <span class="o">-&gt;</span> <span class="kt">String</spa