="type-var">'a</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> <span><span>(<a href="index.html#type-key">key</a> * <span class="type-var">'a</span>)</span> <a href="../../../../../../IStdlib/IContainer/index.html#type-singleton_or_more">IStdlib.IContainer.singleton_or_more</a></span></code></dt><dt class="spec value" id="val-pp_key"><a href="#val-pp_key" class="anchor"></a><code><span class="keyword">val</span> pp_key : <a href="../../../../../../IStdlib/PrettyPrintable/index.html#mo