code: def validate_uniqueness(database_name: str) -> bool:
      database_query = db.session.query(Database).filter(
          Database.database_name == database_name
      )
      return not db.session.query(database_query.exists()).scalar()
  
imports: from __future__ import annotations
  import logging
  from typing import Any
  from superset.daos.base import BaseDAO
  from superset.databases.filters import DatabaseFilter
  from superset.databases.ssh_tunnel.models import SSHTunnel
  from superset.extensions import db
  from superset.models.core import Database
  from superset.models.dashboard import Dashboard
  from superset.models.slice import Slice
  from superset.models.sql_lab import TabState
  from superset.utils.core import DatasourceType
  from superset.utils.ssh_tunnel import unmask_password_info
label_desc: Use image node_id 2 for calling the DatabaseDAO obj's underlying member method code with example usage: obj.validate_uniqueness(database_name) and returns: unknown