code: def test_fillna_int(self):
      ser = Series(np.random.default_rng(2).integers(-100, 100, 50))
      return_value = ser.fillna(method="ffill", inplace=True)
      assert return_value is None
      tm.assert_series_equal(
          ser.fillna(method="ffill", inplace=False), ser
      )
  
imports: from datetime import datetime, timedelta, timezone
  import numpy
  import pytest
  import pytz
  from pandas import Categorical, DataFrame, DatetimeIndex, NaT, Period, Series, Timedelta, Timestamp, date_range, isna, timedelta_range
  import pandas._testing
  from pandas.core.arrays import period_array
label_desc: Use image node_id 8 for calling the TestFillnaPad obj's underlying member method code with example usage: obj.test_fillna_int() without return types