code: def test_at_time_raises(self, frame_or_series):
      # GH#20725
      obj = DataFrame([[1, 2, 3], [4, 5, 6]])
      obj = tm.get_obj(obj, frame_or_series)
      msg = "Index must be DatetimeIndex"
      with pytest.raises(
          TypeError, match=msg
      ):  # index is not a DatetimeIndex
          obj.at_time("00:00")
  
file_path: pandas/pandas/tests/frame/methods/test_at_time.py
imports: from datetime import time
  import numpy
  import pytest
  import pytz
  from pandas._libs.tslibs import timezones
  from pandas import DataFrame, date_range
  import pandas._testing
label_desc: Use image node_id 7 for calling the TestAtTime obj's underlying member method code with example usage: obj.test_at_time_raises(frame_or_series) without return types