code: def _execute_discovery_script(self):
      stdout = io.StringIO()
      exit_code = safe_shell_exec.execute(
          self._discovery_script, stdout=stdout
      )
      if exit_code != 0:
          raise RuntimeError(
              "Failed to execute discovery script: {}. Exit code: {}".format(
                  self._discovery_script, exit_code
              )
          )
      return stdout.getvalue()
  
imports: import io
  import logging
  import random
  import threading
  import time
  from collections import defaultdict
  from horovod.runner.common.util import safe_shell_exec
  from horovod.runner.elastic.worker import HostUpdateResult
label_desc: Use image node_id 3 for calling the HostDiscoveryScript obj's underlying member method code with example usage: obj._execute_discovery_script() and returns: stdout