code: def test_to_block_index(self):
      index = BlockIndex(10, [0, 5], [4, 5])
      assert index.to_block_index() is index
  
imports: import operator
  import numpy
  import pytest
  import pandas._libs.sparse
  import pandas.util._test_decorators
  from pandas import Series
  import pandas._testing
  from pandas.core.arrays.sparse import BlockIndex, IntIndex, make_sparse_index
label_desc: Use image node_id 6 for calling the TestBlockIndex obj's underlying member method code with example usage: obj.test_to_block_index() without return types