code: def add_optimizer(trainer, config):
      optimizer = build_optimizer(trainer.model, config)
      trainer.optimizer = optimizer
  
file_path: mmf/tests/trainers/test_utils.py
imports: import os
  import torch
  from mmf.utils.build import build_optimizer
  from mmf.utils.configuration import load_yaml
  from omegaconf import OmegaConf
  from tests.test_utils import SimpleLightningModel, SimpleModel
  from tests.trainers.lightning.lightning_trainer_mock import LightningTrainerMock
  from tests.trainers.test_trainer_mocks import TrainerTrainingLoopMock
label_desc: Use image node_id 4 for calling a global function with example usage: add_optimizer(trainer, config) without return types