Error while migrating tracker store

I’ve tried to migrate the tracker store for rasa x

my endpoint file looks like this:

type: mongo
url: mongodb://
db: rasa

And getting this error:

Traceback (most recent call last):
File "", line 249, in <module>
  File "", line 143, in _migrate_tracker_store_to_rasa_x
    set_latest_event_id(db_session, rasa_x_tracker_store)
  File "", line 204, in set_latest_event_id
    (max_event_id,) = rasa_x_tracker_store.session.query(
AttributeError: 'SQLTrackerStore' object has no attribute 'session'