How to use the @google-cloud/firestore.v1 function in @google-cloud/firestore

// [START fs_schedule_export]
const functions = require('firebase-functions');
const firestore = require('@google-cloud/firestore');
const client = new firestore.v1.FirestoreAdminClient();

// Replace BUCKET_NAME
const bucket = 'gs://BUCKET_NAME';

exports.scheduledFirestoreExport = functions.pubsub
                                            .schedule('every 24 hours')
                                            .onRun((context) => {
  const databaseName = 
    client.databasePath(process.env.GCP_PROJECT, '(default)');

  return client.exportDocuments({
    name: databaseName,
    outputUriPrefix: bucket,
    // Leave collectionIds empty to export all collections
    // or set to a list of collection IDs to export,
    // collectionIds: ['users', 'posts']

get: () => {
        return firestore.v1;
      },
    });