code: def test_constructor_nano(self):
      idx = period_range(
          start=Period(ordinal=1, freq="ns"),
          end=Period(ordinal=4, freq="ns"),
          freq="ns",
      )
      exp = PeriodIndex(
          [
              Period(ordinal=1, freq="ns"),
              Period(ordinal=2, freq="ns"),
              Period(ordinal=3, freq="ns"),
              Period(ordinal=4, freq="ns"),
          ],
          freq="ns",
      )
      tm.assert_index_equal(idx, exp)
  
imports: import numpy
  import pytest
  from pandas._libs.tslibs.period import IncompatibleFrequency
  from pandas.core.dtypes.dtypes import PeriodDtype
  from pandas import Index, NaT, Period, PeriodIndex, Series, date_range, offsets, period_range
  import pandas._testing
  from pandas.core.arrays import PeriodArray
label_desc: Use image node_id 8 for calling the TestPeriodIndex obj's underlying member method code with example usage: obj.test_constructor_nano() without return types