code: def _maybe_apply_main(opdef):
      if opdef.name.lower().endswith(".ipynb") and not opdef.main:
          opdef.main = f"guild.plugins.nbexec {opdef.name}"
  
imports: import ast
  import json
  import logging
  import os
  import re
  from guild import config
  from guild import guildfile
  from guild import model
  from guild import plugin
  from guild import python_util
  from guild import util
  from .None import flags_import_util
label_desc: Use image node_id 2 for calling a global function with example usage: _maybe_apply_main(opdef) without return types