Cannot Create Cloud SQL With DatabaseVersion POSTGRES_12 Using Deployment Manager

According to [documentation](https://cloud.google.com/sql/docs/mysql/admin-api/rest/v1beta4/SqlDatabaseVersion), POSTGRES_12 should be supported? But when I tried to use deployment manager to create Cloud SQL with DatabaseVersion POSTGRES_12, it failed with

```
Manifest expansion encountered the following errors: Invalid properties for 'cloud_sql.py':
'POSTGRES_12' is not one of ['MYSQL_5_5', 'MYSQL_5_6', 'MYSQL_5_7', 'POSTGRES_9_6', 'POSTGRES_11',
'SQLSERVER_ENTERPRISE_2016', 'SQLSERVER_2017_STANDARD', 'SQLSERVER_2017_ENTERPRISE',
'SQLSERVER_2017_EXPRESS', 'SQLSERVER_2017_WEB'] at ['databaseVersion']
```

The cloud_sql.py I'm using is the one from [cloud-foundation-toolkit](https://github.com/GoogleCloudPlatform/cloud-foundation-toolkit/blob/master/dm/templates/cloud_sql/cloud_sql.py).

Is this a bug or did I miss something?

Thank you very much for your help!