Map">PPMap</a>.key = <a href="../Symbol/index.html#type-t">Symbol.t</a></code></span></summary><dl><dt class="spec type" id="type-key"><a href="#type-key" class="anchor"></a><code><span class="keyword">type</span> key</code><code> = <a href="../Symbol/index.html#type-t">Symbol.t</a></code></dt><dt class="spec type" id="type-t"><a href="#type-t" class="anchor"></a><code><span class="keyword">type</span> <span>+'a t</span></code></dt></dl><dl><dt class="spec value" id="val-empty"><a href="#val-empty" class="a