docs: def run_migrations_online():
      """Run migrations in 'online' mode.
  
      In this scenario we need to create an Engine
      and associate a connection with the context.
  
      """
      alembic_config = config.get_section(config.config_ini_section)
      alembic_config['sqlalchemy.url'] = os.environ['DATABASE_URI']
  
      connectable = engine_from_config(
          alembic_config,
          prefix='sqlalchemy.',
          poolclass=pool.NullPool)
  
      with connectable.connect() as connection:
          context.configure(
              connection=connection,
              target_metadata=target_metadata
          )
  
          with context.begin_transaction():
              context.run_migrations()