code: def optim_creator(model, config):
      optimizer = optim.SGD(
          model.parameters(),
          lr=config.get("lr", 0.001),
          momentum=config.get("momentum", 0.9),
      )
      return optimizer
  
imports: import pytest
  import logging
  from unittest import TestCase
  import ray
  from ray.data import Dataset
  import torch.nn
  import torch.optim
  from bigdl.orca import init_orca_context, stop_orca_context
  from bigdl.orca.learn.pytorch import Estimator
  from bigdl.orca.learn.metrics import MSE
label_desc: Use image node_id 4 for calling a global function with example usage: optim_creator(model, config) and returns: optimizer