code: def test_drop_inplace_no_leftover_column_reference(self):
      # GH 13934
      df = DataFrame(
          {"a": [1, 2, 3]}, columns=Index(["a"], dtype="object")
      )
      a = df.a
      df.drop(["a"], axis=1, inplace=True)
      tm.assert_index_equal(df.columns, Index([], dtype="object"))
      a -= a.mean()
      tm.assert_index_equal(df.columns, Index([], dtype="object"))
  
imports: import re
  import numpy
  import pytest
  from pandas.errors import PerformanceWarning
  import pandas
  from pandas import DataFrame, DatetimeIndex, Index, MultiIndex, Series, Timestamp
  import pandas._testing
label_desc: Use image node_id 21 for calling the TestDataFrameDrop obj's underlying member method code with example usage: obj.test_drop_inplace_no_leftover_column_reference() without return types