src/util.js
function isMultisource(arg) {
	return Array.isArray(arg) &&
		!(typeof arg[0] === 'number' && (arg.length === 1 || typeof arg[1] === 'number')) &&
		!(arg.length < 32 && arg.every(ch => Array.isArray(ch) || ArrayBuffer.isView(ch)))
}
function isMultisource(arg) {
	return Array.isArray(arg) &&
		!(typeof arg[0] === 'number' && (arg.length === 1 || typeof arg[1] === 'number')) &&
		!(arg.length < 32 && arg.every(ch => Array.isArray(ch) || ArrayBuffer.isView(ch)))
}
if source is multisource