code: def _validate_lambda_api_key(self, api_key: str):
      client = api_client.LambdaAPIClient(api_key=api_key)
      if not client.validate_api_key():
          raise_invalid_credentials_error(fields=[["creds", "api_key"]])
  
imports: import json
  from typing import List
  from requests import HTTPError
  from dstack._internal.core.backends.base import Backend
  from dstack._internal.core.backends.lambdalabs import LambdaBackend, api_client
  from dstack._internal.core.backends.lambdalabs.config import LambdaConfig
  from dstack._internal.core.errors import BackendInvalidCredentialsError
  from dstack._internal.core.models.backends.base import BackendType, ConfigElementValue, ConfigMultiElement
  from dstack._internal.core.models.backends.lambdalabs import AnyLambdaConfigInfo, LambdaConfigInfo, LambdaConfigInfoWithCreds, LambdaConfigInfoWithCredsPartial, LambdaConfigValues, LambdaCreds, LambdaStoredConfig
  from dstack._internal.server.models import BackendModel, ProjectModel
  from dstack._internal.server.services.backends.configurators.base import Configurator, raise_invalid_credentials_error
label_desc: Use image node_id 7 for calling the LambdaConfigurator obj's underlying member method code with example usage: obj._validate_lambda_api_key(api_key) without return types