code: def init_multi_net_def(model_file):
      mace_check(
          os.path.isfile(model_file),
          "Input graph file '" + model_file + "' does not exist!",
      )
      multi_net_def = mace_pb2.MultiNetDef()
      with open(model_file, "rb") as f:
          multi_net_def.ParseFromString(f.read())
      return multi_net_def
  
imports: import argparse
  import copy
  import os
  import sh
  import yaml
  from py_proto import mace_pb2
  from transform.base_converter import ConverterUtil
  from transform.base_converter import MaceKeyword
  from transform.base_converter import MaceOp
  from transform.hexagon_converter import HexagonOp
  from utils.config_parser import DataFormat
  from utils.config_parser import ModelKeys
  from utils.util import mace_check
label_desc: Use image node_id 3 for calling a global function with example usage: init_multi_net_def(model_file) and returns: multi_net_def