code: def test_isnull_notnull_docstrings():
      # GH#41855 make sure its clear these are aliases
      doc = pd.DataFrame.notnull.__doc__
      assert doc.startswith(
          "\nDataFrame.notnull is an alias for DataFrame.notna.\n"
      )
      doc = pd.DataFrame.isnull.__doc__
      assert doc.startswith(
          "\nDataFrame.isnull is an alias for DataFrame.isna.\n"
      )
  
      doc = Series.notnull.__doc__
      assert doc.startswith(
          "\nSeries.notnull is an alias for Series.notna.\n"
      )
      doc = Series.isnull.__doc__
      assert doc.startswith(
          "\nSeries.isnull is an alias for Series.isna.\n"
      )
  
file_path: pandas/pandas/tests/base/test_misc.py
imports: import sys
  import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas.compat import PYPY
  from pandas.core.dtypes.common import is_dtype_equal, is_object_dtype
  import pandas
  from pandas import Index, Series
label_desc: Use image node_id 1 for calling a global function with example usage: test_isnull_notnull_docstrings() without return types