_&quot; or &quot;_M_&quot; (internal field of std::thread::id)</p></div></div><div class="odoc-spec"><div class="spec module anchored" id="module-Set"><a href="#module-Set" class="anchor"></a><code><span><span class="keyword">module</span> <a href="Set/index.html">Set</a></span><span> : <a href="../../IStdlib/PrettyPrintable/module-type-PPSet/index.html">IStdlib.PrettyPrintable.PPSet</a> <span class="keyword">with</span> <span><span class="keyword">type</span> <a href="../../IStdlib/PrettyPrintable/module-t