code: def test_getitem_index(self):
      self.assertListEqual(self.s2c[1], [(0, 2), (1, 5), (2, 8)])
  
imports: import logging
  import unittest
  import numpy
  from numpy.testing import assert_array_equal
  from scipy import sparse
  from scipy.sparse import csc_matrix
  from scipy.special import psi
  import gensim.matutils
label_desc: Use image node_id 3 for calling the TestSparse2Corpus obj's underlying member method code with example usage: obj.test_getitem_index() without return types