How to use the lsat-js.Lsat.fromToken function in lsat-js

export default async function paywall(
  req: Request,
  res: Response,
  next: NextFunction
): Promise {
  const { headers } = req
  const hodl = req.boltwallConfig ? req.boltwallConfig.hodl : false

  // If missing LSAT in request to protected content
  // then we need to create a new invoice and corresponding LSAT
  let lsat: Lsat | undefined = undefined
  if (headers.authorization) {
    try {
      lsat = Lsat.fromToken(headers.authorization)
    } catch (e) {
      req.logger.error(
        'Could not create LSAT from given authorization header: %s. Error: %s',
        headers.authorization,
        e.message
      )
    }
  }

  if (!headers.authorization || !lsat || lsat.isExpired()) {
    let invoice: InvoiceResponse
    try {
      invoice = await createInvoice(req)
    } catch (e) {
      // handle ln-service errors
      if (Array.isArray(e)) {

return next({
      message:
        'Request malformed: Expected a 256-bit string for the payment hash',
    })
  }

  // if no LSAT then it depends on the route for how to handle it
  if (!headers.authorization || !headers.authorization.includes('LSAT')) {
    return next()
  }

  // if we have an lsat header
  // need  make sure the lsat is properly encoded
  let lsat: Lsat
  try {
    lsat = Lsat.fromToken(headers.authorization)
    assert(lsat, 'Could not decode lsat from authorization header')
  } catch (e) {
    req.logger.debug(
      `Received malformed LSAT authorization header from ${req.hostname}: ${headers.authorization}`
    )
    req.logger.error(e)
    res.status(400)
    return next({ message: `Bad Request: Malformed LSAT header.`, details: e })
  }

  if (lsat.isExpired()) {
    req.logger.debug(
      `Request made with expired LSAT for ${req.originalUrl} from ${req.hostname}`
    )
    res.status(401)
    return next({