> <span>&#45;&gt;</span> <span>bg:<span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span><span class="type-var">'e</span> list</span> <span>&#45;&gt;</span> <span>(<span><span>(<span class="type-var">'c</span>, <span class="type-var">'d</span>)</span> Stdlib.result</span> <span>&#45;&gt;</span> unit)</span> <span>&#45;&gt;</span> <span>unit Lwt.t</span>)</span></span> <span>&#45;&gt;</span> <span>?&#8288;onclose:<span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span>unit Lwt.t</