code: def test_asof_nanosecond_index_access(self):
      ts = Timestamp("20130101").as_unit("ns")._value
      dti = DatetimeIndex([ts + 50 + i for i in range(100)])
      ser = Series(
          np.random.default_rng(2).standard_normal(100), index=dti
      )
  
      first_value = ser.asof(ser.index[0])
  
      # GH#46903 previously incorrectly was "day"
      assert dti.resolution == "nanosecond"
  
      # this used to not work bc parsing was done by dateutil that didn't
      #  handle nanoseconds
      assert first_value == ser["2013-01-01 00:00:00.000000050"]
  
      expected_ts = np.datetime64("2013-01-01 00:00:00.000000050", "ns")
      assert first_value == ser[Timestamp(expected_ts)]
  
file_path: pandas/pandas/tests/series/methods/test_asof.py
imports: import numpy
  import pytest
  from pandas._libs.tslibs import IncompatibleFrequency
  from pandas import DatetimeIndex, PeriodIndex, Series, Timestamp, date_range, isna, notna, offsets, period_range
  import pandas._testing
label_desc: Use image node_id 1 for calling the TestSeriesAsof obj's underlying member method code with example usage: obj.test_asof_nanosecond_index_access() without return types