ode></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-apply_subst"><a href="#val-apply_subst" class="anchor"></a><code><span><span class="keyword">val</span> apply_subst : <span><a href="#type-subst">subst</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-t">t</a> option</span></span></code></div></div></details></div><div class="odoc-spec"><div class="spec value anchored" id="val-pp_locks"