code: def flatten(bucket):
      if not imported_flatten_impl:
          import_flatten_impl()
      return flatten_impl(bucket)
  
imports: from collections import OrderedDict
  import copy
  import importlib
  from itertools import chain
  import torch
  import torch.distributed
  from torch.nn.modules import Module
  from torch.autograd import Variable
  from ..multi_tensor_apply import multi_tensor_applier
label_desc: Use image node_id 2 for calling a global function with example usage: flatten(bucket) and returns: flatten_impl