Flask Celery Singleton how?

Question

Python

I want to make the task a singleton.
utils/celery.py

def init_celery(app, celery):
    celery.conf.update(app.config)
    TaskBase = celery.Task

    class ContextTask(TaskBase):
        abstract = True

        def __call__(self, *args, **kwargs):
            with app.app_context():
                return TaskBase.__call__(self, *args, **kwargs)

    celery.Task = ContextTask

tasks.py

class CelerySingleton(celery.Task, Singleton):
    pass

@celery.task(base=CelerySingleton)
def calc():
# при обращении к sqlalchemy получаю
# application not registered on db instance and no application bound to current context

I understand that in tasks.py the CelerySingleton class inherits celery.Task, which is not a ContextTask at all. But how to do it right?