Homepage's starter example doesn't work!

[fhchina]

login.json:

{
	"name": "login",
	"start": "v_Home",
	"vertices": [
		{
			"id": "v_Home"
		},
		{
			"id": "v_LoggedIn"
		}
	],
	"edges": [
		{
			"id": "e_Login",
			"from": "v_Home",
			"to": "v_LoggedIn"
		}
	]
} 

execute command as: graphwalker offline -m login.json "random(edge_coverage(100))"
report error: JSON error: The JSON file is not a valid GraphWalker model: missing top-level "models" array.