code: def test_series_isna():
      s = pd.Series([1, NA], dtype=object)
      expected = pd.Series([False, True])
      tm.assert_series_equal(s.isna(), expected)
  
imports: from datetime import date, time, timedelta
  import pickle
  import numpy
  import pytest
  from pandas._libs.missing import NA
  from pandas.core.dtypes.common import is_scalar
  import pandas
  import pandas._testing
label_desc: Use image node_id 19 for calling a global function with example usage: test_series_isna() without return types