code: def generate_files_string(ntype_list, nodes_file):
      """generate files string"""
      res = ""
      for item in ntype_list:
          res += item + ":" + nodes_file + ","
      return res[:-1]
  
imports: import sys
  import datetime
  import os
  import yaml
  import random
  import shutil
  import six
  import warnings
  import glob
  from collections import defaultdict
  from pgl.utils.logger import log
label_desc: Use image node_id 5 for calling a global function with example usage: generate_files_string(ntype_list, nodes_file) and returns: res