iv>
</section>
        
                <section class="desc markdown">
          <p>Checks that this iterable has only one element, and returns that element.</p>
<p>Throws a <a href="../../dart-core/StateError-class.html">StateError</a> if <code>this</code> is empty or has more than one element.</p>
        </section>
                <section class="summary source-code" id="source">
          <h2><span>Implementation</span></h2>
          <pre class="language-dart"><code class="language-dart">File get sing