code: def test_getitem_returns_view_when_column_is_unique_in_df(
      self, using_copy_on_write, warn_copy_on_write
  ):
      # GH#45316
      df = DataFrame([[1, 2, 3], [4, 5, 6]], columns=["a", "a", "b"])
      df_orig = df.copy()
      view = df["b"]
      with tm.assert_cow_warning(warn_copy_on_write):
          view.loc[:] = 100
      if using_copy_on_write:
          expected = df_orig
      else:
          expected = DataFrame(
              [[1, 2, 100], [4, 5, 100]], columns=["a", "a", "b"]
          )
      tm.assert_frame_equal(df, expected)
  
imports: import re
  import numpy
  import pytest
  from pandas import Categorical, CategoricalDtype, CategoricalIndex, DataFrame, DateOffset, DatetimeIndex, Index, MultiIndex, Series, Timestamp, concat, date_range, get_dummies, period_range
  import pandas._testing
  from pandas.core.arrays import SparseArray
label_desc: Use image node_id 8 for calling the TestGetitemBooleanMask obj's underlying member method code with example usage: obj.test_getitem_returns_view_when_column_is_unique_in_df(using_copy_on_write, warn_copy_on_write) without return types