st</span> <span>&#45;&gt;</span> <span>string option</span> <span>&#45;&gt;</span> bool</code></dt><dt class="spec value" id="val-json"><a href="#val-json" class="anchor"></a><code><span class="keyword">val</span> json : <a href="index.html#type-t">t</a></code></dt><dt class="spec value" id="val-multipart"><a href="#val-multipart" class="anchor"></a><code><span class="keyword">val</span> multipart : <a href="index.html#type-t">t</a></code></dt><dt class="spec value" id="val-content_type_of_file"><a href="#v