text: from sqlalchemy import create_engine
  from sqlalchemy.orm import scoped_session, sessionmaker
  from sqlalchemy.ext.declarative import declarative_base
  engine = create_engine('sqlite:///myairports.db', convert_unicode=True)
  db_session = scoped_session(sessionmaker(autocommit=False,
                                           autoflush=False,
                                           bind=engine))
  Base = declarative_base()
  Base.query = db_session.query_property()
  def init_db():
      import models
      Base.metadata.create_all(bind=engine)
  