def get_pk(self, model: Optional[Type[Model]] = None):
        """
        Get the model primary key SQLAlchemy column.
        Will not support composite keys
        """
        model_ = model or self.obj
        pk_name = self._get_pk_name(model_)
        if pk_name and isinstance(pk_name, str):
            return getattr(model_, pk_name)
        return None

        Get the model primary key SQLAlchemy column.
        Will not support composite keys
        
flask_appbuilder/models/sqla/interface.py