code: def test_batch_call():
      a = Batch(torch.tensor(42), 0)
      b = Batch((torch.tensor(42), torch.tensor(21)), 0)
  
      def f(x):
          return x
  
      assert a.call(f).atomic
      assert not b.call(f).atomic
  
file_path: fairscale/tests/nn/pipe/test_microbatch.py
imports: import pytest
  import torch
  import torch.cuda
  from fairscale.nn.pipe.microbatch import Batch, check, gather, scatter
label_desc: Use image node_id 3 for calling a global function with example usage: test_batch_call() and returns: x