```rust
use appwrite::Client;
use appwrite::services::Messaging;
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let client = Client::new();
client.set_endpoint("https://<REGION>.cloud.appwrite.io/v1"); // Your API Endpoint
client.set_project("<YOUR_PROJECT_ID>"); // Your project ID
client.set_key("<YOUR_API_KEY>"); // Your secret API key
let messaging = Messaging::new(&client);
let result = messaging.list_subscribers(
"<TOPIC_ID>",
Some(vec![]), // optional
Some("<SEARCH>"), // optional
Some(false) // optional
).await?;
let _ = result;
Ok(())
}
```