Prevent adding the same worker run as a dependency of another multiple times

process = cli.request('CreateProcess', body={'corpus': SOME_CORPUS_ID})
run1 = cli.request('CreateWorkerRun', id=process['id'], body={'parents': [], 'worker_version_id': SOME_VERSION_ID})
run2 = cli.request('CreateWorkerRun', id=process['id'], body={'parents': [], 'worker_version_id': OTHER_VERSION_ID})

cli.request('PartialUpdateWorkerRun', id=run2['id'], body={'parents': [run1['id']] * 42})