code: def test_combine_first_empty_columns():
      left = DataFrame(columns=["a", "b"])
      right = DataFrame(columns=["a", "c"])
      result = left.combine_first(right)
      expected = DataFrame(columns=["a", "b", "c"])
      tm.assert_frame_equal(result, expected)
  
imports: from datetime import datetime
  import numpy
  import pytest
  from pandas.core.dtypes.cast import find_common_type
  from pandas.core.dtypes.common import is_dtype_equal
  import pandas
  from pandas import DataFrame, Index, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 8 for calling a global function with example usage: test_combine_first_empty_columns() without return types