code: def test_nan_as_null(version):
      # Create a nan that is not numpy.nan
      values = np.array(["foo", np.nan, np.nan * 2, "bar"] * 10)
      df = pd.DataFrame({"strings": values})
      _check_pandas_roundtrip(df, version=version)
  
imports: import io
  import os
  import sys
  import tempfile
  import pytest
  import hypothesis
  import hypothesis.strategies
  import numpy
  import pyarrow
  import pyarrow.tests.strategies
  from pyarrow.feather import read_feather, write_feather, read_table, FeatherDataset
label_desc: Use image node_id 29 for calling a global function with example usage: test_nan_as_null(version) without return types