="type-annotation">K</span> <span class="parameter-name">key</span></span>)
    </section>
    <section class="desc markdown">
      <p>Get the first key in the map that is strictly larger than <code>key</code>. Returns
<code>null</code> if no key was not found.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span> </h2>
      <pre class="language-dart"><code class="language-dart">K firstKeyAfter(K key) {
  if (key == null) throw new ArgumentErro