code: def __init__(self, schedule):
      self._schedule = schedule
      self._generator = self.host_generator()
  
imports: from contextlib import contextmanager
  import psutil
  import os
  import socket
  import mock
  import pytest
  import ray
  from horovod.common.util import gloo_built
  from horovod.runner.elastic.discovery import HostDiscovery
  from horovod.ray.elastic_v2 import RayHostDiscovery
  from horovod.ray.runner import RayExecutor
label_desc: Use image node_id 1 to create a new SimpleTestDiscovery object from inherited base classes: HostDiscovery with example: obj = SimpleTestDiscovery(schedule)