code: def test_astype(self):
      # GH 13149, GH 13209
      idx = TimedeltaIndex([1e14, "NaT", NaT, np.nan], name="idx")
  
      result = idx.astype(object)
      expected = Index(
          [Timedelta("1 days 03:46:40")] + [NaT] * 3,
          dtype=object,
          name="idx",
      )
      tm.assert_index_equal(result, expected)
  
      result = idx.astype(np.int64)
      expected = Index(
          [100000000000000] + [-9223372036854775808] * 3,
          dtype=np.int64,
          name="idx",
      )
      tm.assert_index_equal(result, expected)
  
      result = idx.astype(str)
      expected = Index([str(x) for x in idx], name="idx", dtype=object)
      tm.assert_index_equal(result, expected)
  
      rng = timedelta_range("1 days", periods=10)
      result = rng.astype("i8")
      tm.assert_index_equal(result, Index(rng.asi8))
      tm.assert_numpy_array_equal(rng.asi8, result.values)
  
file_path: pandas/pandas/tests/indexes/timedeltas/methods/test_astype.py
imports: from datetime import timedelta
  import numpy
  import pytest
  import pandas
  from pandas import Index, NaT, Timedelta, TimedeltaIndex, timedelta_range
  import pandas._testing
  from pandas.core.arrays import TimedeltaArray
label_desc: Use image node_id 3 for calling the TestTimedeltaIndex obj's underlying member method code with example usage: obj.test_astype() without return types