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{

		Description:    "The request signature we calculated does not match the signature you provided. Check your key and signing method.",
		HTTPStatusCode: http.StatusForbidden,
	},
	ErrMethodNotAllowed: {
		Code:           "MethodNotAllowed",
		Description:    "The specified method is not allowed against this resource.",
		HTTPStatusCode: http.StatusMethodNotAllowed,
	},
	ErrInvalidPart: {
		Code:           "InvalidPart",

	// resource was not supported by the code - for instance, attempting to delete a resource that
	// can only be created. API calls that return MethodNotAllowed can never succeed.
	// Status code 405
	StatusReasonMethodNotAllowed StatusReason = "MethodNotAllowed"

	// StatusReasonNotAcceptable means that the accept types indicated by the client were not acceptable

	for _, res := range results {
		err := res.err
		if err == nil {
			return res.oi, res.zIdx, nil
		}
		if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) {
			// some errors such as MethodNotAllowed for delete marker
			// should be returned upwards.
			return res.oi, res.zIdx, err
		}
		// When its a delete marker and versionID is empty
		// we should simply return the error right away.

// TestSomeUnimplementedRESTStorage ensures that if a rest.Storage does
// not implement a given method, that it is literally not registered
// with the server. We need to have at least one verb supported inorder
// to get a MethodNotAllowed rather than NotFound error.
func TestSomeUnimplementedRESTStorage(t *testing.T) {
	type T struct {
		Method  string
		Path    string
		ErrCode int
	}

	cases := map[string]T{