code: def test_slice_unique():
      """
      Raise ValueError if the index is not unique.
      """
      not_unique = pd.DataFrame(
          [], index=["code", "code2", "code1", "code"]
      )
      with pytest.raises(
          ValueError,
          match="Non-unique Index labels should be monotonic increasing.",
      ):
          not_unique.select_rows(slice("code", "code2"))
  
imports: import datetime
  import re
  import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 12 for calling a global function with example usage: test_slice_unique() without return types