code: def test_scatter_index_one():
      it = chainermn.datasets.scatter._scatter_index(10, 3, False)
      split = [(0, 0, 4), (1, 4, 7), (2, 7, 10)]
      for lhs, rhs in zip(split, it):
          assert lhs == rhs
  
imports: from __future__ import with_statement
  import itertools
  import unittest
  import mpi4py.MPI
  import numpy
  import pytest
  from chainer import testing
  import chainermn
  from chainermn.communicators.flat_communicator import FlatCommunicator
  from chainermn.communicators.naive_communicator import NaiveCommunicator
  import chainerx
label_desc: Use image node_id 4 for calling a global function with example usage: test_scatter_index_one() without return types