code: def run_migrations_online():
      
      connectable = context.config.attributes.get("connection", None)
  
      if connectable is None:
          options = context.config.get_section(context.config.config_ini_section)
          url = options.pop("url")
          connectable = create_engine(url, poolclass=pool.NullPool)
  
      with connectable.connect() as connection:
          context.configure(
              connection=connection,
              target_metadata=db.metadata,
              compare_server_default=True,
          )
          with context.begin_transaction():
              context.run_migrations()
docs: Run migrations in 'online' mode.
  
      In this scenario we need to create an Engine
      and associate a connection with the context.