[
{ "_id" : 0, "name" : "Betty Boop",
             "subjects" : [
                { "type" : "optional", "subject" : "Voice"},
                { "type" : "required", "subject" : "Math" },
                { "type" : "required", "subject" : "English" } ]
},
{ "_id" : 1, "name" : "Donald Duck",
             "subjects" : [
                { "type" : "optional", "subject" : "Accounting" },
                { "type" : "required", "subject" : "Math" },
                { "type" : "required", "subject" : "English" } ]
}
]