code: def between(min_value, max_value):
      
      def validate(value):
          if value < min_value:
              return e("{} is not greater than or equal to {}",
                  value, min_value)
          if value > max_value:
              return e("{} is not less than or equal to {}",
                  value, max_value)
      return validate
docs: Validates that a field value is between the two values
      given to this validator.