function tables(connection) {
    if (!connection.database || connection.database === '') {
        return [];
    }

    const client = pool.getClient(connection);

    return client
        .dataset(connection.database)
        .getTables()
        .then(results => {
            return (results[0] || []).map(table => table.id);
        });
}
Should return a list of tables that are in the database
@param {object} connection - Connection Parameters
@param {string} connection.projectId - Google Cloud Project Id
@param {string} connection.database - Google Big Query Database
@param {string} connection.keyFilename - Google Service Account Key File
@returns {Promise} that resolves to an array of table names