docstr: Initialize the paired chunk.
docstr_tok: ["Initialize","the","paired","chunk","."]
code: def init_pair(self, friend_chunk: "Chunk") -> None:
      """Initialize the paired chunk."""
      if (
          self.paired_chunk is None
          and friend_chunk.paired_chunk is None
      ):
          self.paired_chunk = friend_chunk
          friend_chunk.paired_chunk = self
      else:
          assert self.paired_chunk is friend_chunk
          assert friend_chunk.paired_chunk is self
  
imports: from dataclasses import dataclass
  from enum import Enum
  from typing import Dict, List, Optional
  import torch
  import torch.distributed
  from torch.distributed import ProcessGroup
  from colossalai.utils import get_current_device
  from colossalai.utils.device import IS_NPU_AVAILABLE
label_desc: Use image node_id 21 for calling the Chunk obj's underlying member method code with example usage: obj.init_pair(friend_chunk) without return types