docs: def validate(self, value, model=None, context=None):
          """
          Validate
          Perform value validation and return result
  
          :param value:           value to check
          :param model:           parent model being validated
          :param context:         object or None, validation context
          :return:                shiftschema.results.SimpleResult
          """
  
          regex = self.regex()
          match = regex.match(value)
          if not match:
              return Error(self.not_email)
  
          # success otherwise
          return Error()