Return a reference to the interface this provider's proxy objects actually
   * implement. If any of the methods on this interface are annotated as being
   * {@link Idempotent} or {@link AtMostOnce}, then this fact will be passed to
   * the {@link RetryPolicy#shouldRetry(Exception, int, int, boolean)} method on
   * error, for use in determining whether or not failover should be attempted.
Return a reference to the interface this provider's proxy objects actually
   * implement. If any of the methods on this interface are annotated as being
   * {@link Idempotent} or {@link AtMostOnce}, then this fact will be passed to
   * the {@link RetryPolicy#shouldRetry(Exception, int, int, boolean)} method on
   * error, for use in determining whether or not failover should be attempted. | FailoverProxyProvider.java