code: def test_astype_td64_to_string(self, frame_or_series):
      # GH#41409
      tdi = pd.timedelta_range("1 Day", periods=3)
      obj = frame_or_series(tdi)
  
      expected = frame_or_series(
          ["1 days", "2 days", "3 days"], dtype="string"
      )
      result = obj.astype("string")
      tm.assert_equal(result, expected)
  
imports: import re
  import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import Categorical, CategoricalDtype, DataFrame, DatetimeTZDtype, Index, Interval, IntervalDtype, NaT, Series, Timedelta, Timestamp, concat, date_range, option_context
  import pandas._testing
label_desc: Use image node_id 37 for calling the TestAstype obj's underlying member method code with example usage: obj.test_astype_td64_to_string(frame_or_series) without return types