docs: def validate_wrap(self, value):
          ''' Validates the type and length of ``value`` '''
          if not isinstance(value, basestring):
              self._fail_validation_type(value, basestring)
          if self.max is not None and len(value) > self.max:
              self._fail_validation(value, 'Value too long (%d)' % len(value))
          if self.min is not None and len(value) < self.min:
              self._fail_validation(value, 'Value too short (%d)' % len(value))