code: def test_fillna_aligns(self):
      s1 = Series([0, 1, 2], list("abc"))
      s2 = Series([0, np.nan, 2], list("bac"))
      result = s2.fillna(s1)
      expected = Series([0, 0, 2.0], list("bac"))
      tm.assert_series_equal(result, expected)
  
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 5 for calling the TestSeriesFillNA obj's underlying member method code with example usage: obj.test_fillna_aligns() without return types