code: def get_account_db_class(cls) -> Type[BaseAccountDB]:
          
          if cls.account_db_class is None:
              raise AttributeError("No account_db_class set for {0}".format(cls.__name__))
          return cls.account_db_class
docs: Return the :class:`~eth.db.account.BaseAccountDB` class that the
          state class uses.