$type operator
--------------

Analyze the collection `video.moviesScratch`. What can
you say about the `_id` field?

Find those documents whose `_id` is a string (i.e., not an ObjectId).

    db.moviesScratch.find({_id: {$type: "string"}})

See also https://docs.mongodb.com/manual/reference/operator/query/type/ .


Find those documents whose `_id` is an ObjectId:

    TODO...