code: def test_astype_float_to_period(self):
      result = Series([np.nan]).astype("period[D]")
      expected = Series([NaT], dtype="period[D]")
      tm.assert_series_equal(result, expected)
  
imports: from datetime import datetime, timedelta
  from importlib import reload
  import string
  import sys
  import numpy
  import pytest
  from pandas._libs.tslibs import iNaT
  import pandas.util._test_decorators
  from pandas import NA, Categorical, CategoricalDtype, DatetimeTZDtype, Index, Interval, NaT, Series, Timedelta, Timestamp, cut, date_range, to_datetime
  import pandas._testing
label_desc: Use image node_id 5 for calling the TestAstype obj's underlying member method code with example usage: obj.test_astype_float_to_period() without return types