nbsp;<span class="keyword">val</span>&nbsp;read_lock&nbsp;:&nbsp;(unit&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;with_switch_backup&nbsp;:&nbsp;string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;(<span class="constructor">OpamState</span>.state&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit<br>
&nbsp;&nbsp;<span class="key