code: def test_dtype_mangle_dup_cols_single_dtype(all_parsers):
      # GH#42022
      parser = all_parsers
      data = """a,a\n1,1"""
      result = parser.read_csv(StringIO(data), dtype=str)
      expected = DataFrame({"a": ["1"], "a.1": ["1"]})
      tm.assert_frame_equal(result, expected)
  
imports: from collections import defaultdict
  from io import StringIO
  import numpy
  import pytest
  from pandas.errors import ParserWarning
  import pandas
  from pandas import DataFrame, Timestamp
  import pandas._testing
  from pandas.core.arrays import ArrowStringArray, IntegerArray, StringArray
label_desc: Use image node_id 15 for calling a global function with example usage: test_dtype_mangle_dup_cols_single_dtype(all_parsers) without return types