code: def _add_roles_to_policy(
      self, policy: Dict, service_account_email: str, roles: List[str]
  ):
      member = f"serviceAccount:{service_account_email}"
      for role in roles:
          policy["bindings"].append({"role": role, "members": [member]})
  
imports: import json
  from typing import Dict, List
  import googleapiclient.discovery
  import googleapiclient.errors
  from google.auth.credentials import Credentials
  from dstack._internal.core.backends.gcp import GCPBackend, auth
  from dstack._internal.core.backends.gcp import utils
  from dstack._internal.core.backends.gcp.config import GCPConfig
  from dstack._internal.core.errors import BackendAuthError, ServerClientError
  from dstack._internal.core.models.backends.base import BackendType, ConfigElement, ConfigElementValue, ConfigMultiElement
  from dstack._internal.core.models.backends.gcp import AnyGCPConfigInfo, GCPConfigInfo, GCPConfigInfoWithCreds, GCPConfigInfoWithCredsPartial, GCPConfigValues, GCPCreds, GCPDefaultCreds, GCPServiceAccountCreds, GCPStoredConfig
  from dstack._internal.server import settings
  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 12 for calling the GCPConfigurator obj's underlying member method code with example usage: obj._add_roles_to_policy(policy, service_account_email, roles) without return types