code: def test_astype_timedelta64(self):
      # GH 13149, GH 13209
      idx = TimedeltaIndex([1e14, "NaT", NaT, np.nan])
  
      msg = (
          r"Cannot convert from timedelta64\[ns\] to timedelta64. "
          "Supported resolutions are 's', 'ms', 'us', 'ns'"
      )
      with pytest.raises(ValueError, match=msg):
          idx.astype("timedelta64")
  
      result = idx.astype("timedelta64[ns]")
      tm.assert_index_equal(result, idx)
      assert result is not idx
  
      result = idx.astype("timedelta64[ns]", copy=False)
      tm.assert_index_equal(result, idx)
      assert result is idx
  
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 5 for calling the TestTimedeltaIndex obj's underlying member method code with example usage: obj.test_astype_timedelta64() without return types