swift 如何设置EaseUI聊天的气泡背景

[[EaseBaseMessageCell appearance] setSendBubbleBackgroundImage:[[UIImage imageNamed:@"EaseUIResource.bundle/chat_sender_bg"] stretchableImageWithLeftCapWidth:5 topCapHeight:35]];

    [[EaseBaseMessageCell appearance] setRecvBubbleBackgroundImage:[[UIImage imageNamed:@"EaseUIResource.bundle/chat_receiver_bg"] stretchableImageWithLeftCapWidth:35 topCapHeight:35]];

if let image = UIImage(named: "sendBubbleBackgroundImage") {

            EaseMessageCell.appearance().sendBubbleBackgroundImage = image

}