n> option</span> <span class="arrow">&#45;&gt;</span></span> <span class="type-var">'b</span></span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-assert_none"><a href="#val-assert_none" class="anchor"></a><code><span><span class="keyword">val</span> assert_none : <span><span><span class="type-var">'a</span> option</span> <span class="arrow">&#45;&gt;</span></span> unit</span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-test_from_stri