code: def test_astype_extension_dtypes_duplicate_col(self, dtype):
      # GH#24704
      a1 = Series([0, np.nan, 4], name="a")
      a2 = Series([np.nan, 3, 5], name="a")
      df = concat([a1, a2], axis=1)
  
      result = df.astype(dtype)
      expected = concat([a1.astype(dtype), a2.astype(dtype)], axis=1)
      tm.assert_frame_equal(result, expected)
  
imports: import re
  import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import Categorical, CategoricalDtype, DataFrame, DatetimeTZDtype, Index, Interval, IntervalDtype, NaT, Series, Timedelta, Timestamp, concat, date_range, option_context
  import pandas._testing
label_desc: Use image node_id 17 for calling the TestAstype obj's underlying member method code with example usage: obj.test_astype_extension_dtypes_duplicate_col(dtype) without return types