code: def test_max_nan_bug():
      df = DataFrame(
          {
              "Unnamed: 0": ["-04-23", "-05-06", "-05-07"],
              "Date": [
                  "2013-04-23 00:00:00",
                  "2013-05-06 00:00:00",
                  "2013-05-07 00:00:00",
              ],
              "app": Series([np.nan, np.nan, "OE"]),
              "File": ["log080001.log", "log.log", "xlsx"],
          }
      )
      gb = df.groupby("Date")
      r = gb[["File"]].max()
      e = gb["File"].max().to_frame()
      tm.assert_frame_equal(r, e)
      assert not r["File"].isna().any()
  
imports: import builtins
  import datetime
  from string import ascii_lowercase
  import numpy
  import pytest
  from pandas._libs.tslibs import iNaT
  import pandas
  from pandas import DataFrame, MultiIndex, Series, Timestamp, date_range, isna
  import pandas._testing
  from pandas.util import _test_decorators
label_desc: Use image node_id 31 for calling a global function with example usage: test_max_nan_bug() without return types