def behind(cls):
        """Create a behind variant of this exception."""

        return cls(
            "Database schema is behind the expected revision. "
            "Please upgrade it by running `TruSession().migrate_database()` "
            "or reset it by running `TruSession().reset_database()`.",
            cls.Reason.BEHIND,
        )
Create a behind variant of this exception.
src/core/trulens/core/database/exceptions.py