code: def test_get_loc_nan(self, level, nulls_fixture):
      # GH 18485 : NaN in MultiIndex
      levels = [["a", "b"], ["c", "d"]]
      key = ["b", "d"]
      levels[level] = np.array(
          [0, nulls_fixture], dtype=type(nulls_fixture)
      )
      key[level] = nulls_fixture
      idx = MultiIndex.from_product(levels)
      assert idx.get_loc(tuple(key)) == 3
  
imports: from datetime import timedelta
  import re
  import numpy
  import pytest
  from pandas._libs import index
  from pandas.errors import InvalidIndexError, PerformanceWarning
  import pandas
  from pandas import Categorical, DataFrame, Index, MultiIndex, date_range
  import pandas._testing
label_desc: Use image node_id 7 for calling the TestGetLoc obj's underlying member method code with example usage: obj.test_get_loc_nan(level, nulls_fixture) without return types