code: def test_coalesce_duplicate_columns():
      """
      Test output on duplicate columns.
      """
      df = pd.DataFrame(
          np.array(
              [[1.0, 2.0, 2.0], [np.nan, 3.0, np.nan], [3.0, 1.0, 9.0]]
          ),
          columns=["a", "a", "c"],
      )
  
      expected = pd.DataFrame(
          np.array(
              [[1.0, 2.0, 2.0], [3, 3.0, np.nan], [3.0, 1.0, 9.0]]
          ),
          columns=["a", "a", "c"],
      )
  
      actual = df.coalesce("a")
  
      assert_frame_equal(expected, actual)
  
file_path: pyjanitor/tests/functions/test_coalesce.py
imports: import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 9 for calling a global function with example usage: test_coalesce_duplicate_columns() without return types