code: def test_fillna_col_reordering(self):
      cols = ["COL." + str(i) for i in range(5, 0, -1)]
      data = np.random.default_rng(2).random((20, 5))
      df = DataFrame(index=range(20), columns=cols, data=data)
      msg = "DataFrame.fillna with 'method' is deprecated"
      with tm.assert_produces_warning(FutureWarning, match=msg):
          filled = df.fillna(method="ffill")
      assert df.columns.tolist() == filled.columns.tolist()
  
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 34 for calling the TestFillNA obj's underlying member method code with example usage: obj.test_fillna_col_reordering() without return types