code: def test_at_setitem_multiindex(self):
      df = DataFrame(
          np.zeros((3, 2), dtype="int64"),
          columns=MultiIndex.from_tuples([("a", 0), ("a", 1)]),
      )
      df.at[0, "a"] = 10
      expected = DataFrame(
          [[10, 10], [0, 0], [0, 0]],
          columns=MultiIndex.from_tuples([("a", 0), ("a", 1)]),
      )
      tm.assert_frame_equal(df, expected)
  
imports: from datetime import datetime, timezone
  import numpy
  import pytest
  from pandas.errors import InvalidIndexError
  from pandas import CategoricalDtype, CategoricalIndex, DataFrame, DatetimeIndex, Index, MultiIndex, Series, Timestamp
  import pandas._testing
label_desc: Use image node_id 4 for calling the TestAtSetItem obj's underlying member method code with example usage: obj.test_at_setitem_multiindex() without return types