yword">val</span> return_error : <span>?&#8288;content:<span class="type-var">'a</span></span> <span>&#45;&gt;</span> <span>?&#8288;headers:<span><span>(string * string)</span> list</span></span> <span>&#45;&gt;</span> int <span>&#45;&gt;</span> <span><span><span><span>(<span class="type-var">'b</span>, <span><span class="type-var">'a</span> option</span>)</span> Stdlib.result</span> <a href="Answer/index.html#type-t">Answer.t</a></span> Lwt.t</span></code></dt><dt class="spec value" id="val-verbose"><a hr