Laravel-datatables: Summary total in the footer column

Summary of problem or feature request

How make summary to footer column?

Code snippet of problem

        $dataTableQuery = Users::query()
            ->leftJoin('user_info', 'users.id', '=', 'user_info.id')
            ->select([
                'users.id',
                'users.username',
                'users.role_id',
                'user_info.first_name',
                'user_info.last_name',
                'user_info.email',
                'users.blocked',
                'users.balance',
                'users.created',
            ]);

$sums = [
            'sum_balance' => '0',
        ];

        $datatables = Datatables::of($dataTableQuery )
            ->escapeColumns(['first_name', 'last_name', 'email'])
            ->editColumn('created', function ($user) {
                return Carbon::createFromFormat('Y-m-d H:i:s', $user->created)->toDateString();
            })
            ->editColumn('blocked', function ($user) {
                return $user->blocked_label;
            })
            ->addColumn('actions', function ($user) {
                return $user->gamers_buttons;
            })
            ->filter(function ($query) use ($request) {
                if ($request->has('username')) {
                    $query->where('username', 'like', "%{$request->get('username')}%");
                }
            })
            ->addSum('sum_balance', DB::raw("sum(balance)")) <-- How do it?
            ->with('sums', $sums);

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System details

• Operating System Windows 8.1
• PHP Version 5.6.29
• Laravel Version 5.4
• Laravel-Datatables Version 7