n class="keywordsign">-&gt;</span>&nbsp;bool<br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">end</span><br>
&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;t<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;of_string&nbsp;:&nbsp;string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;to_string&nbsp;:&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;string<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;to_json&nbsp;:&nbsp;t&nbsp;