code: def dummy_input(request, tmpdir_factory):
      """
      Function to create a dummy file
      """
      # Init variables
  
      input_path = tmpdir_factory.mktemp("input_data").join(
          "datasink_test_s3.txt"
      )
  
      # Create input file
      input_path.write_binary(b"ABCD1234")
  
      # Return path
      return str(input_path)
  
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 8 for calling a global function with example usage: dummy_input(request, tmpdir_factory) and returns: str