/span> union : <span><span>(<span><a href="#type-key">key</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-value">value</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-value">value</a> <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> <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</spa