code: def test_round4(self, tz_naive_fixture):
      index = DatetimeIndex(
          ["2016-10-17 12:00:00.001501031"], dtype="M8[ns]"
      )
      result = index.round("10ns")
      expected = DatetimeIndex(
          ["2016-10-17 12:00:00.001501030"], dtype="M8[ns]"
      )
      tm.assert_index_equal(result, expected)
  
      ts = "2016-10-17 12:00:00.001501031"
      dti = DatetimeIndex([ts], dtype="M8[ns]")
      with tm.assert_produces_warning(False):
          dti.round("1010ns")
  
file_path: pandas/pandas/tests/indexes/datetimes/methods/test_round.py
imports: import pytest
  from pandas._libs.tslibs import to_offset
  from pandas._libs.tslibs.offsets import INVALID_FREQ_ERR_MSG
  from pandas import DatetimeIndex, Timestamp, date_range
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestDatetimeIndexRound obj's underlying member method code with example usage: obj.test_round4(tz_naive_fixture) without return types