code: def GetProcessedTaskIdentifiers(self):
      
      if self._storage_type != definitions.STORAGE_TYPE_SESSION:
        raise IOError('Unsupported storage type.')
  
      if not self._processed_task_storage_path:
        raise IOError('Missing processed task storage path.')
  
      return [
          path.replace('.plaso', '')
          for path in os.listdir(self._processed_task_storage_path)]
docs: Identifiers for tasks which have been processed.
  
      Returns:
        list[str]: task identifiers that are processed.
  
      Raises:
        IOError: if the storage type is not supported or
            if the temporary path for the task storage does not exist.
        OSError: if the storage type is not supported or
            if the temporary path for the task storage does not exist.