code: def validate_tag(self, key, value):
          
          if key == 'owner':
              return validate_email(value, self.partial_owner_match)
          elif key == self.gdpr_tag:
              return value in self.gdpr_tag_values
          else:
              return True
docs: Check whether a tag value is valid
  
          Args:
              key: A tag key
              value: A tag value
  
          Returns:
              `(True or False)`
              A boolean indicating whether or not the value is valid