code: def validate_length(self, value):
          
          list_len = len(value) if value else 0
  
          if self.max_length is not None and list_len > self.max_length:
              raise ValidationError(
                  u'List has {} values; max length is {}'.format(list_len, self.max_length))
  
          if self.min_length is not None and list_len < self.min_length:
              raise ValidationError(
                  u'List has {} values; min length is {}'.format(list_len, self.min_length))
docs: Validate the length of value, if min_length or max_length was specified