code: def test_fillna_mixed_type(self, float_string_frame):
      mf = float_string_frame
      mf.loc[mf.index[5:20], "foo"] = np.nan
      mf.loc[mf.index[-10:], "A"] = np.nan
      # TODO: make stronger assertion here, GH 25640
      mf.fillna(value=0)
      msg = "DataFrame.fillna with 'method' is deprecated"
      with tm.assert_produces_warning(FutureWarning, match=msg):
          mf.fillna(method="pad")
  
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 4 for calling the TestFillNA obj's underlying member method code with example usage: obj.test_fillna_mixed_type(float_string_frame) without return types