code: def test_append_different_columns(self, sort):
      df = DataFrame(
          {
              "bools": np.random.default_rng(2).standard_normal(10) > 0,
              "ints": np.random.default_rng(2).integers(0, 10, 10),
              "floats": np.random.default_rng(2).standard_normal(10),
              "strings": ["foo", "bar"] * 5,
          }
      )
  
      a = df[:5].loc[:, ["bools", "ints", "floats"]]
      b = df[5:].loc[:, ["strings", "ints", "floats"]]
  
      appended = a._append(b, sort=sort)
      assert isna(appended["strings"][0:4]).all()
      assert isna(appended["bools"][5:]).all()
  
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 8 for calling the TestAppend obj's underlying member method code with example usage: obj.test_append_different_columns(sort) without return types