On the pythoncode tutorial gmail-api:

googleapiclient.errors.HttpError: <HttpError 400 when requesting https://gmail.googleapis.com/gmail/v1/users/me/messages/batchModify? returned "Number of ids cannot exceed 1000". Details: "[{'message': 'Number of ids cannot exceed 1000', 'domain': 'global', 'reason': 'invalidArgument'}]">