code: def list_platforms() -> str:
      return "\nSupported platforms:\n{}".format(
          "\n".join(get_platforms())
      )
  
file_path: mxnet/ci/build.py
imports: import argparse
  import pprint
  import os
  import signal
  import subprocess
  from itertools import chain
  from subprocess import check_call
  from typing import *
  import yaml
  from util import *
label_desc: Use image node_id 7 for calling a global function with example usage: list_platforms() and returns: str