code: def test_encoding_mmap(memory_map):
      """
      encoding should be working, even when using a memory-mapped file.
  
      GH 23254.
      """
      encoding = "iso8859_1"
      with tm.ensure_clean() as path:
          Path(path).write_bytes(" 1 A Ä 2\n".encode(encoding))
          df = read_fwf(
              path,
              header=None,
              widths=[2, 2, 2, 2],
              encoding=encoding,
              memory_map=memory_map,
          )
      df_reference = DataFrame([[1, "A", "Ä", 2]])
      tm.assert_frame_equal(df, df_reference)
  
imports: from datetime import datetime
  from io import BytesIO, StringIO
  from pathlib import Path
  import numpy
  import pytest
  from pandas.errors import EmptyDataError
  import pandas
  from pandas import DataFrame, DatetimeIndex
  import pandas._testing
  from pandas.core.arrays import ArrowStringArray, StringArray
  from pandas.io.common import urlopen
  from pandas.io.parsers import read_csv, read_fwf
label_desc: Use image node_id 34 for calling a global function with example usage: test_encoding_mmap(memory_map) without return types