code: def get_metrics(config):
      return "accuracy"
  
file_path: analytics-zoo/pyzoo/test/zoo/orca/learn/ray/mxnet/test_mxnet_symbol.py
imports: from unittest import TestCase
  import numpy
  import pytest
  import mxnet
  from zoo.orca.learn.mxnet import Estimator, create_config
label_desc: Use image node_id 4 for calling a global function with example usage: get_metrics(config) and returns: str