code: def test_fillna_overlap(self):
      s = SparseArray([1, np.nan, np.nan, 3, np.nan])
      # filling with existing value doesn't replace existing value with
      # fill_value, i.e. existing 3 remains in sp_values
      res = s.fillna(3)
      exp = np.array([1, 3, 3, 3, 3], dtype=np.float64)
      tm.assert_numpy_array_equal(res.to_dense(), exp)
  
      s = SparseArray([1, np.nan, np.nan, 3, np.nan], fill_value=0)
      res = s.fillna(3)
      exp = SparseArray([1, 3, 3, 3, 3], fill_value=0, dtype=np.float64)
      tm.assert_sp_array_equal(res, exp)
  
imports: import re
  import numpy
  import pytest
  from pandas._libs.sparse import IntIndex
  import pandas
  from pandas import SparseDtype, isna
  import pandas._testing
  from pandas.core.arrays.sparse import SparseArray
label_desc: Use image node_id 12 for calling the TestSparseArray obj's underlying member method code with example usage: obj.test_fillna_overlap() without return types