code: def _flatten(nested_list):
      return [item for list_ in nested_list for item in list_]
  
imports: from abc import ABC, abstractmethod
  from typing import Dict, List
  import torch
  import torchaudio.functional
  from torch import Tensor
  from torchaudio.functional import TokenSpan
label_desc: Use image node_id 3 for calling a global function with example usage: _flatten(nested_list) and returns: unknown