code: def test_dtype_backward_compatibility(self):
      nmf_fname = datapath("nmf_model")
      test_doc = [(0, 1), (1, 1), (2, 1)]
      expected_topics = [(1, 1.0)]
  
      # save model to use in test
      # self.model.save(nmf_fname)
  
      # load a model saved using the latest version of Gensim
      model = nmf.Nmf.load(nmf_fname)
  
      # and test it on a predefined document
      topics = model[test_doc]
      self.assertTrue(np.allclose(expected_topics, topics))
  
imports: import unittest
  import copy
  import logging
  import numbers
  import numpy
  from gensim import matutils
  from gensim.models import nmf
  from gensim.test import basetmtests
  from gensim.test.utils import datapath, get_tmpfile, common_corpus, common_dictionary
label_desc: Use image node_id 13 for calling the TestNmf obj's underlying member method code with example usage: obj.test_dtype_backward_compatibility() without return types