code: def _validate_nebius_creds(self, creds: NebiusCreds):
      try:
          api_client.NebiusAPIClient(json.loads(creds.data)).get_token()
      except requests.HTTPError:
          raise_invalid_credentials_error(fields=[["creds", "data"]])
  
imports: import json
  from typing import List
  import requests
  import dstack._internal.core.backends.nebius.api_client
  from dstack._internal.core.backends.base import Backend
  from dstack._internal.core.backends.nebius import NebiusBackend
  from dstack._internal.core.backends.nebius.config import NebiusConfig
  from dstack._internal.core.models.backends.base import BackendType, ConfigElementValue, ConfigMultiElement
  from dstack._internal.core.models.backends.nebius import NebiusConfigInfo, NebiusConfigInfoWithCreds, NebiusConfigInfoWithCredsPartial, NebiusConfigValues, NebiusCreds, NebiusStoredConfig
  from dstack._internal.server.models import BackendModel, ProjectModel
  from dstack._internal.server.services.backends import Configurator
  from dstack._internal.server.services.backends.configurators.base import raise_invalid_credentials_error
label_desc: Use image node_id 7 for calling the NebiusConfigurator obj's underlying member method code with example usage: obj._validate_nebius_creds(creds) without return types