code: def validate(self) -> None:
      logging.info("Check that the index does not exists anymore")
  
      db = get_db(self.MONGOENGINE_ALIAS)
      collection = db[self.COLLECTION_JOBS]
      ttl_index_names = get_index_names(
          index_information=collection.index_information(),
          field_name=self.field_name,
      )
      if len(ttl_index_names) > 0:
          raise ValueError(
              f"Found TTL index for field {self.field_name}"
          )
  
imports: import logging
  from collections.abc import Mapping
  from typing import Any, Optional
  from libcommon.queue import JobDocument
  from libcommon.simple_cache import CachedResponseDocument
  from mongoengine.connection import get_db
  from mongodb_migration.check import check_documents
  from mongodb_migration.migration import BaseCacheMigration, BaseQueueMigration, CacheMigration, IrreversibleMigrationError, MetricsMigration, QueueMigration
label_desc: Use image node_id 4 for calling the MigrationQueueDeleteTTLIndex obj's underlying member method code with example usage: obj.validate() without return types