code: def test_get_datetime_iso_8601_strlen(self, install_temp):
      # GH#21199
      import checks
  
      # uses NPY_FR_ns
      res = checks.get_datetime_iso_8601_strlen()
      assert res == 48
  
imports: from datetime import datetime
  import os
  import shutil
  import subprocess
  import sys
  import time
  import pytest
  import numpy
  from numpy.testing import IS_WASM
label_desc: Use image node_id 2 for calling the TestDatetimeStrings obj's underlying member method code with example usage: obj.test_get_datetime_iso_8601_strlen(install_temp) without return types