code: def test_fillna_empty(self, using_copy_on_write):
      if using_copy_on_write:
          pytest.skip(
              "condition is unnecessary complex and is deprecated anyway"
          )
      # empty frame (GH#2778)
      df = DataFrame(columns=["x"])
      for m in ["pad", "backfill"]:
          msg = "Series.fillna with 'method' is deprecated"
          with tm.assert_produces_warning(FutureWarning, match=msg):
              df.x.fillna(method=m, inplace=True)
              df.x.fillna(method=m)
  
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 6 for calling the TestFillNA obj's underlying member method code with example usage: obj.test_fillna_empty(using_copy_on_write) without return types