code: def test_freesurfersource():
      fss = nio.FreeSurferSource()
      assert fss.inputs.hemi == "both"
      assert fss.inputs.subject_id == Undefined
      assert fss.inputs.subjects_dir == Undefined
  
imports: import os
  import copy
  import simplejson
  import glob
  import os.path
  from subprocess import Popen
  import hashlib
  from collections import namedtuple
  import pytest
  import nipype
  import nipype.interfaces.io
  from nipype.interfaces.base.traits_extension import isdefined
  from nipype.interfaces.base import Undefined, TraitError
  from nipype.utils.filemanip import dist_is_editable
  from subprocess import check_call, CalledProcessError
label_desc: Use image node_id 18 for calling a global function with example usage: test_freesurfersource() without return types