code: def healthz():
      if app.ready:
          return PlainTextResponse("ok")
      return PlainTextResponse(
          "service unavailable",
          status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
      )
  
file_path: cortex/test/apis/batch/image-classifier-alexnet/app/main.py
imports: import os, json, re
  import requests
  import torch
  import torchvision
  import boto3
  import uuid
  from typing import List
  from PIL import Image
  from io import BytesIO
  from torchvision import transforms
  from fastapi import FastAPI, Request, status
  from fastapi.responses import PlainTextResponse
label_desc: Use image node_id 2 for calling a global function with example usage: healthz() and returns: PlainTextResponse, PlainTextResponse