code: def _builtin_model_op_for_spec(opspec):
      if opspec == "+":
          return DefaultBatchModelProxy(), "+"
      return None
  
file_path: guildai/guild/model_proxy.py
imports: import logging
  import guild
  from guild import guildfile
  from guild import model
  from guild import plugin
label_desc: Use image node_id 3 for calling a global function with example usage: _builtin_model_op_for_spec(opspec) and returns: None, DefaultBatchModelProxy,  str