code: def test_set_index_empty_column(self):
      # GH#1971
      df = DataFrame(
          [
              {"a": 1, "p": 0},
              {"a": 2, "m": 10},
              {"a": 3, "m": 11, "p": 20},
              {"a": 4, "m": 12, "p": 21},
          ],
          columns=["a", "m", "p", "x"],
      )
  
      result = df.set_index(["a", "x"])
  
      expected = df[["m", "p"]]
      expected.index = MultiIndex.from_arrays(
          [df["a"], df["x"]], names=["a", "x"]
      )
      tm.assert_frame_equal(result, expected)
  
imports: from datetime import datetime, timedelta
  import numpy
  import pytest
  from pandas import Categorical, CategoricalIndex, DataFrame, DatetimeIndex, Index, MultiIndex, Series, date_range, period_range, to_datetime
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestSetIndex obj's underlying member method code with example usage: obj.test_set_index_empty_column() without return types