func isErrPreconditionFailed(err error) bool {
	_, ok := err.(PreConditionFailed)
	return ok
}

// isErrMethodNotAllowed - Check if error type is MethodNotAllowed.
func isErrMethodNotAllowed(err error) bool {
	var methodNotAllowed MethodNotAllowed
	return errors.As(err, &methodNotAllowed)
}

func isErrInvalidRange(err error) bool {
	if errors.Is(err, errInvalidRange) {
		return true
	}
	_, ok := err.(InvalidRange)

func enforceRetentionBypassForDelete(ctx context.Context, r *http.Request, bucket string, object ObjectToDelete, oi ObjectInfo, gerr error) error {
	if gerr != nil { // error from GetObjectInfo
		if _, ok := gerr.(MethodNotAllowed); ok {
			// This happens usually for a delete marker
			if oi.DeleteMarker || !oi.VersionPurgeStatus.Empty() {
				// Delete marker should be present and valid.
				return nil
			}
		}

	// If none of the routes match add default error handler routes
	apiRouter.NotFoundHandler = collectAPIStats("notfound", httpTraceAll(errorResponseHandler))
	apiRouter.MethodNotAllowedHandler = collectAPIStats("methodnotallowed", httpTraceAll(methodNotAllowedHandler("S3")))
}

// corsHandler handler for CORS (Cross Origin Resource Sharing)
func corsHandler(handler http.Handler) http.Handler {
	commonS3Headers := []string{