code: def join(input: Tensor, phony: Tensor) -> Tensor:
      """Merges two autograd lanes."""
      if torch.is_grad_enabled() and (
          input.requires_grad or phony.requires_grad
      ):
          input = Join.apply(input, phony)
  
      return input
  
file_path: fairscale/fairscale/nn/pipe/dependency.py
imports: from typing import List, Tuple
  import torch
  from torch import Tensor
  from .phony import get_phony
label_desc: Use image node_id 2 for calling a global function with example usage: join(input, phony) and returns: input