code: def _normalize_modules(modules: _ModulesType):
      if modules is None:
          modules = []
      elif isinstance(modules, str):
          modules = [modules]
      else:
          modules = list(modules)
      modules = ["mars.services"] + modules
      return modules
  
file_path: mars/mars/services/core.py
imports: import abc
  import asyncio
  import enum
  import importlib
  import inspect
  import warnings
  from typing import Dict, Iterable, List, Union
label_desc: Use image node_id 2 for calling a global function with example usage: _normalize_modules(modules) and returns: modules