def _wait_for_workers_to_start(self):
        """Waits for all workers to start."""
        for _ in range(self.workers_count):
            started_indicator = _keep_retrying_while_zmq_again(
                _KEEP_TRYING_WHILE_ZMQ_AGAIN_IS_RAIZED_TIMEOUT_S,
                lambda: self._results_receiver.recv_pyobj(flags=zmq.constants.NOBLOCK))
            assert _WORKER_STARTED_INDICATOR == started_indicator
Waits for all workers to start.
petastorm/workers_pool/process_pool.py