code: def auth_test(self) -> bool:
      try:
          self.get_instances()
          return True
      except requests.HTTPError:
          return False
  
file_path: dstack/src/dstack/_internal/core/backends/vastai/api_client.py
imports: import shlex
  import threading
  import time
  from typing import List, Optional, Union
  import requests
  from requests.adapters import HTTPAdapter, Retry
  import dstack._internal.server.services.docker
  from dstack._internal.core.errors import NoCapacityError
  from dstack._internal.core.models.configurations import RegistryAuth
label_desc: Use image node_id 8 for calling the VastAIAPIClient obj's underlying member method code with example usage: obj.auth_test() and returns: True, False