def _ItemsToUrns(self, items):
    for item in items:
      try:
        yield flow_export.CollectionItemToAff4Path(item)
      except flow_export.ItemNotExportableError:
        pass
Converts collection items to aff4 urns suitable for downloading.
dataset/ETHPy150Open google/grr/grr/gui/api_call_handler_utils.py/CollectionArchiveGenerator._ItemsToUrns