def METHOD_NAME(
    self, worker: Worker, start: bool = True, exclusive: bool = True
) -> None:
    """Add a new worker.
    Args:
        worker: A Worker instance.
        start: Start the worker if True, otherwise the worker must be started manually.
        exclusive: Cancel all workers in the same group as `worker`.
    """
    if exclusive and worker.group:
        self.cancel_group(worker.node, worker.group)
    self._workers.add(worker)
    if start:
        worker._start(self._app, self._remove_worker)