AssertionError: DatabaseBackend is not running Не получается подключиться к postgresql

database.py

SQLALCHEMY_DATABASE_URL = f'postgresql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}: 
{DB_PORT}/{DB_NAME}'


database = Database(SQLALCHEMY_DATABASE_URL)  
metadata = MetaData()
engine = create_engine(SQLALCHEMY_DATABASE_URL)

main.py

from core.database import engine, database, metadata


app = FastAPI()


metadata.create_all(bind=engine)
app.state.database = database


@app.on_event('startup')
async def startup():
    database_ = app.state.database
    if not database_.is_connected:
        await database_.connect()


@app.on_event('shutdown')
async def shutdown():
    database_ = app.state.database
    if database_.is_connected:
        await database_.disconnect()