Access Fauna db v10

Site : https://bbochat.netlify.app

My app accesses a fauna database and the function (db-access.js) that I use relates to Fauna V4

const faunadb = require("faunadb");
const query = faunadb.query;

const client = new faunadb.Client({
    secret: process.env.FAUNADB_SECRET_BBO_CHAT,
    domain: process.env.FAUNADB_DOMAIN,
    port: process.env.FAUNADB_PORT,
    scheme: process.env.FAUNADB_SCHEME,
})

exports.handler = async (key, index) => {
    query_function = query.Map(
        query.Paginate(query.Match(query.Index(index), key)),
        (recordRef) => query.Get(recordRef)
    );
    var response = await client.query(query_function);

    return {
        statusCode: 200,
        body: JSON.stringify(response.data),
    };
}

When I try using the V10 recommendations I get an error

Function db-access has returned an error: faunadb.fql is not a function

But I cannot locate the docs that cover the faunadb object

The V10 code I use is

exports.handler = async (collection, key, index) => {
    query_function = client.query(faunadb.fql`${collection}.${index}(${key}).first()`)
    var response = await client.query(query_function);

    return {
        statusCode: 200,
        body: JSON.stringify(response.data),
    };
}

Sounds like the dependency is not updated. Are you sure you’re using v1 of Fauna client?