def validate(self, value):
        """Validate value."""
        if self.exclusive:
            if value >= self.maximum_value:
                tpl = "'{val}' is bigger or equal than maximum ('{max}')."
                raise ValidationError(
                    tpl.format(val=value, max=self.maximum_value))
        else:
            if value > self.maximum_value:
                raise ValidationError(
                    "'{value}' is bigger than maximum ('{max}').".format(
                        value=value, max=self.maximum_value))