code: def get_fields_for_exception(self, logger, exception):
          
          for klass in getmro(exception.__class__):
              if klass in self.registry:
                  extractor = self.registry[klass]
                  try:
                      return extractor(exception)
                  except:
                      from ._traceback import write_traceback
                      write_traceback(logger)
                      return {}
          return {}
docs: Given an exception instance, return fields to add to the failed action
          message.
  
          @param logger: ``ILogger`` currently being used.
          @param exception: An exception instance.
  
          @return: Dictionary with fields to include.