code: def test_bfill(self, datetime_frame):
      datetime_frame.loc[datetime_frame.index[:5], "A"] = np.nan
      datetime_frame.loc[datetime_frame.index[-5:], "A"] = np.nan
  
      msg = "DataFrame.fillna with 'method' is deprecated"
      with tm.assert_produces_warning(FutureWarning, match=msg):
          alt = datetime_frame.fillna(method="bfill")
  
      tm.assert_frame_equal(datetime_frame.bfill(), alt)
  
imports: import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas import Categorical, DataFrame, DatetimeIndex, NaT, PeriodIndex, Series, TimedeltaIndex, Timestamp, date_range, to_datetime
  import pandas._testing
  from pandas.tests.frame.common import _check_mixed_float
label_desc: Use image node_id 22 for calling the TestFillNA obj's underlying member method code with example usage: obj.test_bfill(datetime_frame) without return types