code: def is_leader(
      pg: Optional[dist.ProcessGroup], leader_rank: int = 0
  ) -> bool:
      """
      Checks if the current processs is the leader.
  
      Args:
          pg (Optional[dist.ProcessGroup]): the process's rank within the pg is used to
              determine if the process is the leader. pg being None implies that the
              process is the only member in the group (e.g. a single process program).
          leader_rank (int): the definition of leader (defaults to 0). The caller can
              override it with a context-specific definition.
      """
      if pg is None:
          return leader_rank == 0
      return pg.rank() == leader_rank
  
imports: from functools import wraps
  from typing import Any, Callable, cast, Optional, TypeVar
  import torch.distributed
label_desc: Use image node_id 1 for calling a global function with example usage: is_leader(pg, leader_rank) and returns: unknown, unknown