code: def test_drop_nonunique(self):
      df = DataFrame(
          [
              ["x-a", "x", "a", 1.5],
              ["x-a", "x", "a", 1.2],
              ["z-c", "z", "c", 3.1],
              ["x-a", "x", "a", 4.1],
              ["x-b", "x", "b", 5.1],
              ["x-b", "x", "b", 4.1],
              ["x-b", "x", "b", 2.2],
              ["y-a", "y", "a", 1.2],
              ["z-b", "z", "b", 2.1],
          ],
          columns=["var1", "var2", "var3", "var4"],
      )
  
      grp_size = df.groupby("var1").size()
      drop_idx = grp_size.loc[grp_size == 1]
  
      idf = df.set_index(["var1", "var2", "var3"])
  
      # it works! GH#2101
      result = idf.drop(drop_idx.index, level=0).reset_index()
      expected = df[-df.var1.isin(drop_idx.index)]
  
      result.index = expected.index
  
      tm.assert_frame_equal(result, expected)
  
imports: import re
  import numpy
  import pytest
  from pandas.errors import PerformanceWarning
  import pandas
  from pandas import DataFrame, DatetimeIndex, Index, MultiIndex, Series, Timestamp
  import pandas._testing
label_desc: Use image node_id 11 for calling the TestDataFrameDrop obj's underlying member method code with example usage: obj.test_drop_nonunique() without return types