```kotlin
    if (response.responseCount >= 3) {
      return null // If we've failed 3 times, give up.
    }
    ```

    This above code relies on this `responseCount` extension val:

    ```kotlin
    val Response.responseCount: Int
      get() = generateSequence(this) { it.priorResponse }.count()
    ```

 * to limit the retries by the class of errors and number of attempts.  To get the number of
 * attempts to the current point use this function.
 *
 * ```java
 * private int responseCount(Response response) {
 *   int result = 1;
 *   while ((response = response.priorResponse()) != null) {
 *     result++;
 *   }
 *   return result;
 * }
 * ```
 *