if pdh not in self.collections:
self.collections[pdh] = arvados.collection.CollectionReader(pdh, api_client=self.api_client,
keep_client=self.keep_client)
if pdh not in self.collections:
self.collections[pdh] = arvados.collection.CollectionReader(pdh, api_client=self.api_client,
keep_client=self.keep_client)