code: def down_ec2(instance_id, region, access_key_id, secret_access_key):
      
      conn = connect_to_ec2(region, access_key_id, secret_access_key)
      # get the instance_id from the state file, and stop the instance
      instance = conn.stop_instances(instance_ids=instance_id)[0]
      while instance.state != "stopped":
          log_yellow("Instance state: %s" % instance.state)
          sleep(10)
          instance.update()
      log_green('Instance state: %s' % instance.state)
docs: shutdown of an existing EC2 instance