pan><span><span class="type-var">'a</span> <a href="#type-t">t</a></span> <span class="arrow">&#45;&gt;</span></span> <span><span class="label">init</span>:<span class="type-var">'b</span> <span class="arrow">&#45;&gt;</span></span> <span><span class="label">f</span>:<span>(<span><a href="#type-key">key</a> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'b</span> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'a</span> <span class="arrow">&#45;&gt;</span><