code: def test_reset_index_duplicate_columns_default(
      self, multiindex_df, flag
  ):
      df = multiindex_df.rename_axis("A")
      df = df.set_flags(allows_duplicate_labels=flag)
  
      msg = r"cannot insert \('A', ''\), already exists"
      with pytest.raises(ValueError, match=msg):
          df.reset_index()
  
imports: from datetime import datetime
  from itertools import product
  import numpy
  import pytest
  from pandas.core.dtypes.common import is_float_dtype, is_integer_dtype
  import pandas
  from pandas import Categorical, CategoricalIndex, DataFrame, Index, Interval, IntervalIndex, MultiIndex, RangeIndex, Series, Timestamp, cut, date_range
  import pandas._testing
label_desc: Use image node_id 18 for calling the TestResetIndex obj's underlying member method code with example usage: obj.test_reset_index_duplicate_columns_default(multiindex_df, flag) without return types