code: def test_getitem_nat(self):
      idx = PeriodIndex(["2011-01", "NaT", "2011-02"], freq="M")
      assert idx[0] == Period("2011-01", freq="M")
      assert idx[1] is NaT
  
      s = Series([0, 1, 2], index=idx)
      assert s[NaT] == 1
  
      s = Series(idx, index=idx)
      assert s[Period("2011-01", freq="M")] == Period(
          "2011-01", freq="M"
      )
      assert s[NaT] is NaT
  
imports: from datetime import datetime
  import re
  import numpy
  import pytest
  from pandas._libs.tslibs import period
  from pandas.errors import InvalidIndexError
  import pandas
  from pandas import DatetimeIndex, NaT, Period, PeriodIndex, Series, Timedelta, date_range, notna, period_range
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestGetItem obj's underlying member method code with example usage: obj.test_getitem_nat() without return types