How do I create a mongoose CSV dump that includes population?

My function definition looks like:

String#export(Schema, callback, options)

I want to convert the Mongoose Schema into a String CSV repersentation including any population specified in the options. You can assume that the population specification is stored like so:

options.population {
    path: "_creator",
    selection: "email"
}

The population should be repersented by the CSV like so:

_id, name, _creator_email
"123", "Foo", "foo@bar.com"

As you can see I want to prefix the path before the field.

Note: The callback definition is:

Void#callback(err,csv_string)

Can someone please provide me with code or a library capable of doing this. The function definitions can change if it makes it easier to accomplish.