Upload a file to a File Upload Field through API

Upload a file to a File Upload Field through API

Hello,

Is there any way to upload a file to a custom file upload field in a module when doing an Update using the Record API?

I've found and I am able to upload files to attachments but I don't know how to upload them to a field. I've checked the documentation at 
but the File Upload field type does not appear in the examples.

Thanks

    Nederlandse Hulpbronnen