sent</code> must not add or remove keys from the map.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span></h2>
      <pre class="language-dart"><code class="language-dart">V putIfAbsent(K key, V ifAbsent()) {
  if (containsKey(key)) {
    return this[key];
  }
  return this[key] = ifAbsent();
}</code></pre>
    </section>

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