code: def test_add_column_already_exists(dataframe):
      """column already exists"""
      with pytest.raises(
          ValueError,
          match="Attempted to add column that already exists",
      ):
          dataframe.add_column("a", 42)
  
file_path: pyjanitor/tests/functions/test_add_column.py
imports: import numpy
  import pandas
  import pytest
  from hypothesis import given, settings
  from hypothesis import strategies
  from pandas.testing import assert_series_equal
  from janitor.testing_utils.strategies import df_strategy
label_desc: Use image node_id 2 for calling a global function with example usage: test_add_column_already_exists(dataframe) without return types