y sending back a
 <a href="../core/Response.Status.html#SERVICE_UNAVAILABLE"><code>HTTP 503 (Service unavailable)</code></a> error response with a
 <code>Retry-After</code> header set to the value provided by the method parameter.
 </p>
 <p>
 Invoking a <code>cancel(...)</code> method multiple times to cancel request processing has the same effect as canceling
 the request processing only once. Invoking a <code>cancel(...)</code> method on an asynchronous response instance that has
 already been cancelled o