def __init__(
        self, datamodel: BaseInterface, col_name: str, message: Optional[str] = None
    ) -> None:
        """
        :param datamodel: The datamodel class, abstract layer for backend
        :param col_name: The unique column name.
        :param message: The error message.
        """
        self.datamodel = datamodel
        self.col_name = col_name
        self.message = message

        :param datamodel: The datamodel class, abstract layer for backend
        :param col_name: The unique column name.
        :param message: The error message.
        
flask_appbuilder/validators.py