HostedRotationLambda & Transform

I'm trying to implement aws secrets rotation with with the serverless framework (https://alexharv074.github.io/2020/11/23/adding-hosted-rotation-lambda-to-a-database-stack.html)

  AppGraphqDbAppsSecretRotationSchedule:
    Type: AWS::SecretsManager::RotationSchedule
    Properties:
      SecretId: !Ref AppGraphqlDbAppsSecretsManagerSecret
      HostedRotationLambda:
        RotationType: PostgreSQLSingleUser
      RotationRules:
        AutomaticallyAfterDays: 30

I get the error

 To use the HostedRotationLambda property, you must use the AWS::SecretsManager transform.

How can I add "transform"? Below a working Aws cloudformation template

AWSTemplateFormatVersion: 2010-09-09
Description: Rotation Lambda example stack
Transform: AWS::SecretsManager-2020-07-23

Parameters: {}

Resources: