code: def test_fillna_dont_cast_strings(self):
      # GH#9043
      # make sure a string representation of int/float values can be filled
      # correctly without raising errors or being converted
      vals = ["0", "1.5", "-0.3"]
      for val in vals:
          ser = Series([0, 1, np.nan, np.nan, 4], dtype="float64")
          result = ser.fillna(val)
          expected = Series([0, 1, val, val, 4], dtype="object")
          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 7 for calling the TestSeriesFillNA obj's underlying member method code with example usage: obj.test_fillna_dont_cast_strings() without return types