a href="#val-update" class="anchor"></a><code><span><span class="keyword">val</span> update : <span><a href="#type-key">key</a> <span class="arrow">&#45;&gt;</span></span> <span><span>( <span><span><a href="#type-value">value</a> option</span> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-value">value</a> option</span> )</span> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span> <a href="#type-t">t</a></span></code></div></