old_contents: import sqlalchemy.ext.declarative
  import sqlalchemy.orm
  
  from conf import settings
  
  engine = sqlalchemy.create_engine(settings['DB_URL'])
  
  db_session = sqlalchemy.orm.scoped_session(
      sqlalchemy.orm.sessionmaker(
          autocommit=False,
          autoflush=False,
          bind=engine,
      )
  )
  
  Base = sqlalchemy.ext.declarative.declarative_base()
  Base.query = db_session.query_property()
  
new_contents: import sqlalchemy.ext.declarative
  import sqlalchemy.orm
  
  from conf import settings
  
  engine = sqlalchemy.create_engine(settings['DB_URL'])
  
  db_session = sqlalchemy.orm.scoped_session(
      sqlalchemy.orm.sessionmaker(
          autocommit=False,
          autoflush=False,
          bind=engine,
      )
  )
  
  Base = sqlalchemy.ext.declarative.declarative_base()
  Base.query = db_session.query_property()
  
  def create_tables():
      import models
      Base.metadata.create_all(bind=engine)
  
  def drop_tables():
      import models
      Base.metadata.drop_all(bind=engine)
  
subject: Add create_tables, drop_tables helpers