code: def test_append_new_columns(self):
      # see gh-6129: new columns
      df = DataFrame({"a": {"x": 1, "y": 2}, "b": {"x": 3, "y": 4}})
      row = Series([5, 6, 7], index=["a", "b", "c"], name="z")
      expected = DataFrame(
          {
              "a": {"x": 1, "y": 2, "z": 5},
              "b": {"x": 3, "y": 4, "z": 6},
              "c": {"z": 7},
          }
      )
      result = df._append(row)
      tm.assert_frame_equal(result, expected)
  
imports: import datetime
  from itertools import combinations
  import dateutil
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Index, Series, Timestamp, concat, isna
  import pandas._testing
label_desc: Use image node_id 4 for calling the TestAppend obj's underlying member method code with example usage: obj.test_append_new_columns() without return types