code: def test_drop_not_lexsorted():
      # GH 12078
  
      # define the lexsorted version of the multi-index
      tuples = [("a", ""), ("b1", "c1"), ("b2", "c2")]
      lexsorted_mi = MultiIndex.from_tuples(tuples, names=["b", "c"])
      assert lexsorted_mi._is_lexsorted()
  
      # and the not-lexsorted version
      df = pd.DataFrame(
          columns=["a", "b", "c", "d"],
          data=[[1, "b1", "c1", 3], [1, "b2", "c2", 4]],
      )
      df = df.pivot_table(index="a", columns=["b", "c"], values="d")
      df = df.reset_index()
      not_lexsorted_mi = df.columns
      assert not not_lexsorted_mi._is_lexsorted()
  
      # compare the results
      tm.assert_index_equal(lexsorted_mi, not_lexsorted_mi)
      with tm.assert_produces_warning(PerformanceWarning):
          tm.assert_index_equal(
              lexsorted_mi.drop("a"), not_lexsorted_mi.drop("a")
          )
  
file_path: pandas/pandas/tests/indexes/multi/test_drop.py
imports: import numpy
  import pytest
  from pandas.errors import PerformanceWarning
  import pandas
  from pandas import Index, MultiIndex
  import pandas._testing
label_desc: Use image node_id 4 for calling a global function with example usage: test_drop_not_lexsorted() without return types