code: def test_invalid_dtype_backend():
      msg = (
          "dtype_backend numpy is invalid, only 'numpy_nullable' and "
          "'pyarrow' are allowed."
      )
      with pytest.raises(ValueError, match=msg):
          read_fwf("test", dtype_backend="numpy")
  
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 43 for calling a global function with example usage: test_invalid_dtype_backend() without return types