code: def test_round_dst_border_nonexistent(
      self, method, ts_str, freq, unit
  ):
      # GH 23324 round near "spring forward" DST
      ts = Timestamp(ts_str, tz="America/Chicago").as_unit(unit)
      result = getattr(ts, method)(freq, nonexistent="shift_forward")
      expected = Timestamp("2018-03-11 03:00:00", tz="America/Chicago")
      assert result == expected
      assert (
          result._creso
          == getattr(NpyDatetimeUnit, f"NPY_FR_{unit}").value
      )
  
      result = getattr(ts, method)(freq, nonexistent="NaT")
      assert result is NaT
  
      msg = "2018-03-11 02:00:00"
      with pytest.raises(pytz.NonExistentTimeError, match=msg):
          getattr(ts, method)(freq, nonexistent="raise")
  
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 13 for calling the TestTimestampRound obj's underlying member method code with example usage: obj.test_round_dst_border_nonexistent(method, ts_str, freq, unit) without return types