Whether the value passes validation

        Args:
            value (obj) : the value to validate against this property type

        Returns:
            True if valid, False otherwise

def is_valid(self, value):
        ''' Whether the value passes validation

        Args:
            value (obj) : the value to validate against this property type

        Returns:
            True if valid, False otherwise

        '''
        try:
            if validation_on():
                self.validate(value, False)
        except ValueError:
            return False
        else:
            return True