code: def test_astype(self):
      # GH 13149, GH 13209
      idx = DatetimeIndex(
          ["2016-05-16", "NaT", NaT, np.nan], dtype="M8[ns]", name="idx"
      )
  
      result = idx.astype(object)
      expected = Index(
          [Timestamp("2016-05-16")] + [NaT] * 3,
          dtype=object,
          name="idx",
      )
      tm.assert_index_equal(result, expected)
  
      result = idx.astype(np.int64)
      expected = Index(
          [1463356800000000000] + [-9223372036854775808] * 3,
          dtype=np.int64,
          name="idx",
      )
      tm.assert_index_equal(result, expected)
  
imports: from datetime import datetime
  import dateutil
  import numpy
  import pytest
  import pytz
  import pandas
  from pandas import DatetimeIndex, Index, NaT, PeriodIndex, Timestamp, date_range
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestDatetimeIndex obj's underlying member method code with example usage: obj.test_astype() without return types