def _on_event(self, event):
        """
        Returns the referential action for a given database operation
        on the referenced table the foreign key constraint is associated with.

        :param event: Name of the database operation/event to return the referential action for.
        :type event: str

        :rtype: str or None
        """
        if self.has_option(event):
            on_event = self.get_option(event).upper()

            if on_event not in ["NO ACTION", "RESTRICT"]:
                return on_event

        return False
def _on_event ( self , event ) : if self . has_option ( event ) : on_event = self . get_option ( event ) . upper ( ) if on_event not in [ "NO ACTION" , "RESTRICT" ] : return on_event return False
Returns the referential action for a given database operation
        on the referenced table the foreign key constraint is associated with.

        :param event: Name of the database operation/event to return the referential action for.
        :type event: str

        :rtype: str or None