sp;<span class="keyword">of</span>&nbsp;string&nbsp;list&nbsp;*&nbsp;(string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keywordsign">|</span>&nbsp;<span class="constructor">Rest</span>&nbsp;<span class="keyword">of</span>&nbsp;(string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)
&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;key&nbsp;=&nbsp;string
&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;doc&nbsp;=&nbsp;string
&nbsp;&nbsp;<span class="