code: def test_combine_generic(self, float_frame):
      df1 = float_frame
      df2 = float_frame.loc[float_frame.index[:-5], ["A", "B", "C"]]
  
      combined = df1.combine(df2, np.add)
      combined2 = df2.combine(df1, np.add)
      assert combined["D"].isna().all()
      assert combined2["D"].isna().all()
  
      chunk = combined.loc[combined.index[:-5], ["A", "B", "C"]]
      chunk2 = combined2.loc[combined2.index[:-5], ["A", "B", "C"]]
  
      exp = (
          float_frame.loc[
              float_frame.index[:-5], ["A", "B", "C"]
          ].reindex_like(chunk)
          * 2
      )
      tm.assert_frame_equal(chunk, exp)
      tm.assert_frame_equal(chunk2, exp)
  
imports: import numpy
  import pytest
  import pandas
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestCombine obj's underlying member method code with example usage: obj.test_combine_generic(float_frame) without return types