// make invoice
const invoice = await SmartyPayAPI.createInvoice({
  expiresAt: new Date(Date.now() + 1000 * 60 * 60), // after 1 hour from now
  amount: '1.99 bUSDT', // see valid tokens here: https://docs.smartypay.io/general/supported-tokens
}, {
  secretKey: 'YOUR_SECRET_KEY', // you can get it here: https://dashboard.smartypay.io/
  publicKey: 'YOUR_API_KEY', // you can get it here: https://dashboard.smartypay.io/
});