code: def test_fillna_invalid_method(self, float_frame):
      with pytest.raises(ValueError, match="ffil"):
          float_frame.fillna(method="ffil")
  
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 32 for calling the TestFillNA obj's underlying member method code with example usage: obj.test_fillna_invalid_method(float_frame) without return types