code: def test_empty_column_names(df):
      """Return dataframe if `column_names` is empty."""
      assert_frame_equal(df.coalesce(), df)
  
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 6 for calling a global function with example usage: test_empty_column_names(df) without return types