is method.
If the <a href="../../dart-collection/SplayTreeSet/contains.html">contains</a> method is computed,
rather than being based on an actual object instance,
then there may not be a specific object instance representing the
set element.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span></h2>
      <pre class="language-dart"><code class="language-dart">E lookup(Object object) {
  if (!_validKey(object)) return null;
  int comp = _splay(ob