class_docstr: Create a local autoscaling cluster for testing.
  
  See test_autoscaler_fake_multinode.py for an end-to-end example.
docstr: Start the cluster.
  
  After this call returns, you can connect to the cluster with
  ray.init("auto").
docstr_tok: ["Start","the","cluster",".","After","this","call","returns",",","you","can","connect","to","the","cluster","with","ray.init","(","``","auto","''",")","."]
code: def start(
      self, _system_config=None, override_env: Optional[Dict] = None
  ):
      """Start the cluster.
  
      After this call returns, you can connect to the cluster with
      ray.init("auto").
      """
      subprocess.check_call(["ray", "stop", "--force"])
      _, fake_config = tempfile.mkstemp()
      with open(fake_config, "w") as f:
          f.write(json.dumps(self._config))
      cmd = [
          "ray",
          "start",
          "--autoscaling-config={}".format(fake_config),
          "--head",
      ]
      if "CPU" in self._head_resources:
          cmd.append(
              "--num-cpus={}".format(self._head_resources.pop("CPU"))
          )
      if "GPU" in self._head_resources:
          cmd.append(
              "--num-gpus={}".format(self._head_resources.pop("GPU"))
          )
      if "object_store_memory" in self._head_resources:
          cmd.append(
              "--object-store-memory={}".format(
                  self._head_resources.pop("object_store_memory")
              )
          )
      if self._head_resources:
          cmd.append(
              "--resources='{}'".format(
                  json.dumps(self._head_resources)
              )
          )
      if _system_config is not None:
          cmd.append(
              "--system-config={}".format(
                  json.dumps(_system_config, separators=(",", ":"))
              )
          )
      env = os.environ.copy()
      env.update(
          {"AUTOSCALER_UPDATE_INTERVAL_S": "1", "RAY_FAKE_CLUSTER": "1"}
      )
      if override_env:
          env.update(override_env)
      subprocess.check_call(cmd, env=env)
  
imports: import copy
  import json
  import logging
  import os
  import subprocess
  import tempfile
  import time
  from typing import Dict, Optional
  import yaml
  import ray
  import ray._private.services
  from ray._private import ray_constants
  from ray._private.client_mode_hook import disable_client_hook
  from ray._raylet import GcsClientOptions
  from ray.util.annotations import DeveloperAPI
label_desc: Use image node_id 3 for calling the AutoscalingCluster obj's underlying member method code with example usage: obj.start(_system_config, override_env) without return types