pan> <span style="white-space:nowrap">key:<a class="type" title="String - The basic String class." href="../../String.html">String</a></span>):<a class="type" title="Bool - The standard Boolean type, which can either be true or false." href="../../Bool.html">Bool</a></code></h3><div class="doc"><p>Returns <code><a href="../../Bool.html">true</a></code> if <code>key</code> is mapped, <code><a href="../../Bool.html">false</a></code> otherwise.</p></div></div><div class="field "><a name="get"></a><h3 class="an