Object-class.html">Object</a></span> <span class="parameter-name">needle</span></span>)
            <span class="returntype parameter">&#8594; <a href="dart-async/Future-class.html">Future</a><span class="signature">&lt;<wbr><span class="type-parameter"><a href="dart-core/bool-class.html">bool</a></span>&gt;</span></span>
          </span>
                  </dt>
        <dd class="inherited">
          Returns whether <code>needle</code> occurs in the elements provided by this stream. <a href="dart-async/S