How to create Batch document

import 'package:dart_appwrite/dart_appwrite.dart';
import 'dart:convert';

Future<void> start(final req, final res) async {
   final client = new Client();
   final database = Databases(client);

  if (req.variables['APPWRITE_FUNCTION_ENDPOINT'] == null ||
      req.variables['APPWRITE_FUNCTION_API_KEY'] == null) {
    print("Environment variables are not set. Function cannot use Appwrite SDK.");
    } else {
        client
            .setEndpoint(req.variables['APPWRITE_FUNCTION_ENDPOINT'])
            .setProject(req.variables['APPWRITE_FUNCTION_PROJECT_ID'])
            .setKey(req.variables['APPWRITE_FUNCTION_API_KEY'])
            .setSelfSigned(true);
    }

    try {
        final documents = jsonDecode(req.variables.APPWRITE_FUNCTION_DATA);
        final userID = req.APPWRITE_FUNCTION_USER_ID ?? '';
      
        // check Document structure
        documents.forEach((doc)=>{
        //TODO: Add user id
        //TODO: Add permission
         await database.createDocument('[DATABASE_ID]', '[COLLECTION_ID]', '[DOCUMENT_ID]', doc);
        });
     res.json({areDevelopersAwesome: true,});
    } catch (e) {
     res.json({areDevelopersAwesome: false,});
    }
};