particular spec.
Parameters:
      * role (str) -- user-defined role for the workers with
        this spec
  * **local_world_size** (*int*) -- number local workers to run

  * **fn** (*Optional**[**Callable**]*) -- (deprecated use
    entrypoint instead)

  * **entrypoint** (*Optional**[**Union**[**Callable**,
    **str**]**]*) -- worker function or command

  * **args** (*Tuple*) -- arguments to pass to "entrypoint"

  * **rdzv_handler** (*RendezvousHandler*) -- handles rdzv for
    this set of workers

  * **max_restarts** (*int*) -- number of max retries for the
    workers

  * **monitor_interval** (*float*) -- monitor status of workers
    every "n" seconds

  * **master_port** (*Optional**[**int**]*) -- fixed port to run
    the c10d store on rank 0 if not specified then will chose a
    random free port

  * **master_addr** (*Optional**[**str**]*) -- fixed master_addr
