How to use the hafas-client/stringify.accessibility function in hafas-client

const journeys = (from, to, opt) => {
	from = location(from)
	to = location(to)

	opt = opt || {}
	opt.products = Object.assign({}, defaults.products, opt.products)
	opt = Object.assign({}, defaults, opt)
	opt.when = opt.when || new Date()

	const filters = [
		  _stringify.products(opt.products)
		, stringify.accessibility[opt.accessibility]
	]
	if (opt.bike) filters.push(stringify.bike)
	// todo: add req.gisFltrL

	return request({
		  cfg: {polyEnc: 'GPA'}
		, meth: 'TripSearch'
		, req: {
			  outDate: _stringify.date(opt.when)
			, outTime: _stringify.time(opt.when)
			, numF: opt.results
			, getPasslist: opt.passedStations
			, maxChg: opt.transfers
			, minChgTime: opt.transferTime
			, depLocL: [from]
			, viaLocL: opt.via ? [{loc: {type: 'S', lid: 'L=' + opt.via}}] : null