code: def test_add_mismatched_reso_doesnt_downcast(self):
      # https://github.com/pandas-dev/pandas/pull/48748#issuecomment-1260181008
      td = pd.Timedelta(microseconds=1)
      dti = pd.date_range("2016-01-01", periods=3) - td
      dta = dti._data.as_unit("us")
  
      res = dta + td.as_unit("us")
      # even though the result is an even number of days
      #  (so we _could_ downcast to unit="s"), we do not.
      assert res.unit == "us"
  
imports: from __future__ import annotations
  from datetime import timedelta
  import operator
  import numpy
  import pytest
  from pandas._libs.tslibs import tz_compare
  from pandas.core.dtypes.dtypes import DatetimeTZDtype
  import pandas
  import pandas._testing
  from pandas.core.arrays import DatetimeArray, TimedeltaArray
label_desc: Use image node_id 18 for calling the TestNonNano obj's underlying member method code with example usage: obj.test_add_mismatched_reso_doesnt_downcast() without return types