n>&nbsp;perm&nbsp;:&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int&nbsp;option<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;create&nbsp;:&nbsp;<span class="constructor">Base</span>.t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t<br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">end</span><br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;to_attri