code: def test_maybe_convert_i8_nat(self, breaks):
      # GH 20636
      index = IntervalIndex.from_breaks(breaks)
  
      to_convert = breaks._constructor([pd.NaT] * 3).as_unit("ns")
      expected = Index([np.nan] * 3, dtype=np.float64)
      result = index._maybe_convert_i8(to_convert)
      tm.assert_index_equal(result, expected)
  
      to_convert = to_convert.insert(0, breaks[0])
      expected = expected.insert(0, float(breaks[0]._value))
      result = index._maybe_convert_i8(to_convert)
      tm.assert_index_equal(result, expected)
  
imports: from itertools import permutations
  import re
  import numpy
  import pytest
  import pandas
  from pandas import Index, Interval, IntervalIndex, Timedelta, Timestamp, date_range, interval_range, isna, notna, timedelta_range
  import pandas._testing
  import pandas.core.common
label_desc: Use image node_id 14 for calling the TestIntervalIndex obj's underlying member method code with example usage: obj.test_maybe_convert_i8_nat(breaks) without return types