code: def test_round_subsecond(self):
      # GH#14440 & GH#15578
      result = Timestamp("2016-10-17 12:00:00.0015").round("ms")
      expected = Timestamp("2016-10-17 12:00:00.002000")
      assert result == expected
  
      result = Timestamp("2016-10-17 12:00:00.00149").round("ms")
      expected = Timestamp("2016-10-17 12:00:00.001000")
      assert result == expected
  
      ts = Timestamp("2016-10-17 12:00:00.0015")
      for freq in ["us", "ns"]:
          assert ts == ts.round(freq)
  
      result = Timestamp("2016-10-17 12:00:00.001501031").round("10ns")
      expected = Timestamp("2016-10-17 12:00:00.001501030")
      assert result == expected
  
imports: from hypothesis import given, strategies
  import numpy
  import pytest
  import pytz
  from pandas._libs import lib
  from pandas._libs.tslibs import NaT, OutOfBoundsDatetime, Timedelta, Timestamp, iNaT, to_offset
  from pandas._libs.tslibs.dtypes import NpyDatetimeUnit
  from pandas._libs.tslibs.period import INVALID_FREQ_ERR_MSG
  import pandas._testing
label_desc: Use image node_id 5 for calling the TestTimestampRound obj's underlying member method code with example usage: obj.test_round_subsecond() without return types