def METHOD_NAME(self) -> None:
    if len(self.procs) > 0:
        raise RuntimeError("The launcher can only create subprocesses once.")
    if self.cluster_environment.local_rank() != 0:
        raise RuntimeError(
            "Lightning attempted to launch new distributed processes with `local_rank > 0`. This should not happen."
            " Possible reasons: 1) LOCAL_RANK environment variable was incorrectly modified by the user,"
            " 2) `ClusterEnvironment.creates_processes_externally` incorrectly implemented."
        )