code: def test_where_none(self):
      # GH 4667
      # setting with None changes dtype
      df = DataFrame({"series": Series(range(10))}).astype(float)
      df[df > 7] = None
      expected = DataFrame(
          {"series": Series([0, 1, 2, 3, 4, 5, 6, 7, np.nan, np.nan])}
      )
      tm.assert_frame_equal(df, expected)
  
      # GH 7656
      df = DataFrame(
          [
              {"A": 1, "B": np.nan, "C": "Test"},
              {"A": np.nan, "B": "Test", "C": np.nan},
          ]
      )
  
      orig = df.copy()
  
      mask = ~isna(df)
      df.where(mask, None, inplace=True)
      expected = DataFrame(
          {
              "A": [1.0, np.nan],
              "B": [None, "Test"],
              "C": ["Test", None],
          }
      )
      tm.assert_frame_equal(df, expected)
  
      df = orig.copy()
      df[~mask] = None
      tm.assert_frame_equal(df, expected)
  
imports: from datetime import datetime
  from hypothesis import given
  import numpy
  import pytest
  from pandas.core.dtypes.common import is_scalar
  import pandas
  from pandas import DataFrame, DatetimeIndex, Index, Series, StringDtype, Timestamp, date_range, isna
  import pandas._testing
  from pandas._testing._hypothesis import OPTIONAL_ONE_OF_ALL
label_desc: Use image node_id 16 for calling the TestDataFrameIndexingWhere obj's underlying member method code with example usage: obj.test_where_none() without return types