sdk-for-dart/docs/examples/proxy/create-function-rule.md

import 'package:dart_appwrite/dart_appwrite.dart';

Client client = Client()
    .setEndpoint('https://<REGION>.cloud.appwrite.io/v1') // Your API Endpoint
    .setProject('<YOUR_PROJECT_ID>') // Your project ID
    .setKey('<YOUR_API_KEY>'); // Your secret API key

Proxy proxy = Proxy(client);

ProxyRule result = await proxy.createFunctionRule(
    domain: '',
    functionId: '<FUNCTION_ID>',
    branch: '<BRANCH>', // (optional)
);