code: def test_replace_replacer_equals_replacement(self):
      # GH 20656
      # make sure all replacers are matching against original values
      s = pd.Series(["a", "b"])
      expected = pd.Series(["b", "a"])
      result = s.replace({"a": "b", "b": "a"})
      tm.assert_series_equal(expected, result)
  
imports: import re
  import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  import pandas
  import pandas._testing
  from pandas.core.arrays import IntervalArray
label_desc: Use image node_id 22 for calling the TestSeriesReplace obj's underlying member method code with example usage: obj.test_replace_replacer_equals_replacement() without return types