[{"_id":"101",parts:["a","b"]},{"_id":"102",parts:["a","c"]},{"_id":"103",parts:["a","z"]},]

db.collection.aggregate([{$project:{diff:{$setDifference:["$parts",["a","b","c"]]},document:"$$ROOT"}},{$match:{"diff":{$eq:[]}}},{$project:{"diff":0}},])