code: def test_unflatten_indexes(self, histogram_indexer):
      # Test if the unflatten indexes method returns a correct nested dictionary of indexes
      indexes = histogram_indexer.unflatten_indexes()
  
      for nid in range(histogram_indexer.node_size):
          for fid in range(histogram_indexer.feature_size):
              for bid in range(
                  histogram_indexer.feature_bin_sizes[fid]
              ):
                  assert indexes[nid][fid][
                      bid
                  ] == histogram_indexer.get_position(nid, fid, bid)
  
file_path: FATE/python/fate/test/histogram/indexer.py
imports: import pytest
  from fate_utils.histogram import HistogramIndexer, Shuffler
label_desc: Use image node_id 13 for calling the TestHistogramIndexer obj's underlying member method code with example usage: obj.test_unflatten_indexes(histogram_indexer) without return types