code: def test_droplevel(self, index_flat):
      # GH 21115
      # MultiIndex is tested separately in test_multi.py
      index = index_flat
  
      assert index.droplevel([]).equals(index)
  
      for level in [index.name, [index.name]]:
          if isinstance(index.name, tuple) and level is index.name:
              # GH 21121 : droplevel with tuple name
              continue
          msg = (
              "Cannot remove 1 levels from an index with 1 levels: at least one "
              "level must be left."
          )
          with pytest.raises(ValueError, match=msg):
              index.droplevel(level)
  
      for level in "wrong", ["wrong"]:
          with pytest.raises(
              KeyError,
              match=r"'Requested level \(wrong\) does not match index name \(None\)'",
          ):
              index.droplevel(level)
  
imports: from copy import copy, deepcopy
  import re
  import numpy
  import pytest
  from pandas.compat import IS64
  from pandas.compat.numpy import np_version_gte1p25
  from pandas.core.dtypes.common import is_integer_dtype, is_numeric_dtype
  import pandas
  from pandas import CategoricalIndex, MultiIndex, PeriodIndex, RangeIndex
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestCommon obj's underlying member method code with example usage: obj.test_droplevel(index_flat) without return types