code: def test_nunique_smoke(self):
      # GH 34019
      n = DataFrame([[1, 2], [1, 2]]).set_index([0, 1]).index.nunique()
      assert n == 1
  
imports: import numpy
  import pytest
  import pandas._libs.index
  from pandas.errors import PerformanceWarning
  import pandas
  from pandas import CategoricalDtype, DataFrame, Index, MultiIndex, Series
  import pandas._testing
  from pandas.core.arrays.boolean import BooleanDtype
label_desc: Use image node_id 11 for calling the TestMultiIndexBasic obj's underlying member method code with example usage: obj.test_nunique_smoke() without return types