You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/matrix-rust-sdk/examples/custom_events/src
    
    the code of the file until where you have to start completion: ///
///  This is an example showcasing how to build a very simple bot with custom
/// events  using the matrix-sdk. To try it, you need a rust build setup, then
/// you can run: `cargo run -p example-custom-events -- <homeserver_url> <user>
/// <password>`
///
/// Use a second client to open a DM to your bot or invite
    
async fn on_regular_room_message(event: OriginalSyncRoomMessageEvent, room: Room) {
    if room.state() != RoomState::Joined {
        return;
    }
    let MessageType::Text(text_content) = event.content.msgtype else { return };

    if text_content.body.contains("!ping") {
        let content = PingEventContent {};

        println!("sending ping");
        room.send(content).await.unwrap();
        println!("ping sent");
    }
}