code: def flatten(input_):
      return _flatten_dense_tensors(input_)
  
file_path: colossalai/colossalai/zero/low_level/_utils.py
imports: import math
  from typing import Optional
  import torch
  import torch.distributed
  from torch._utils import _flatten_dense_tensors, _unflatten_dense_tensors
label_desc: Use image node_id 1 for calling a global function with example usage: flatten(input_) and returns: _flatten_dense_tensors