Python/Flask ImportError: attempted relative import with no known parent package

from models import db
import config
APP = flask.Flask(__name__)
cors = CORS(APP)
APP.config['SQLALCHEMY_DATABASE_URI'] = config.DATABASE_CONNECTION_URI
APP.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
APP.app_context().push()
db.init_app(APP)
db.create_all()