Creating a Private Note with Attachment Using the API

How does one create a private note with an attachment using the API?

The ‘private’ value must be a boolean or the API returns a 400 response.  Attachment uploads should be multipart form data which will stringify the value.

I noticed that all notes with attachments are being created as private notes even without the ‘private’ value set, but I don’t want to rely on that because the API documentation says that ‘private’ should be set to true when creating a private note

There are a few examples online for adding attachments to notes but none of them address the ‘private’ flag, e.g. https://github.com/freshworks/fresh-samples/tree/master/PHP

Thanks