code: def test_ns_index(self):
      nsamples = 400
      ns = int(1e9 / 24414)
      dtstart = np.datetime64("2012-09-20T00:00:00")
  
      dt = dtstart + np.arange(nsamples) * np.timedelta64(ns, "ns")
      freq = ns * offsets.Nano()
      index = DatetimeIndex(dt, freq=freq, name="time")
      self.assert_index_parameters(index)
  
      new_index = date_range(
          start=index[0], end=index[-1], freq=index.freq
      )
      self.assert_index_parameters(new_index)
  
imports: import datetime
  from datetime import date
  import re
  import numpy
  import pytest
  from pandas.compat.numpy import np_long
  import pandas
  from pandas import DataFrame, DatetimeIndex, Index, Timestamp, date_range, offsets
  import pandas._testing
label_desc: Use image node_id 9 for calling the TestDatetimeIndex obj's underlying member method code with example usage: obj.test_ns_index() without return types