is fully asynchronous. Any amount of time can be taken to determine whether the request needs
to be retried. The one requirement is that the completion closure is called to ensure the request is properly
cleaned up after.</p>

                      </div>
                      <div class="declaration">
                        <h4>Declaration</h4>
                        <div class="language">
                          <p class="aside-title">Swift</p>
                          <pre class="highlight swift"><c