<br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">end</span><br>
&nbsp;&nbsp;<span class="keyword">module</span>&nbsp;<span class="constructor">Map</span>&nbsp;:<br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">sig</span><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;key&nbsp;=&nbsp;t<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;+<span class="keywordsign">'</span>a&nbsp;t<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">val</s