Mage2\Checkout\Controllers\CheckoutController::billingAddress PHP Method

    public function billingAddress()
    {
        $user = Auth::user();
        $countries = Country::all();
        $address = Address::where('user_id', '=', $user->id)->where('type', '=', 'BILLING')->get()->first();
        if (null === $address) {
            $address = new Address();
        }
        return view('checkout.billing-address')->with('address', $address)->with('countries', $countries);
    }