code: def validate(self, 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))
docs: Validate value.