A guide on how to duplicate layers from another PSD

[okuma10]

I want to apply a PSD with an overlay template(that I plan to toggle it's visibility with Python based on some data) to an image. So far I created a new document and applied the "add image as layer" but how do I copy the layers from the template?
I managed to open the template document via Session.app.open() (that changed the active document but I suppose it should be fine).
But there are no examples of transferring layers from one document to another.
Can anyone help?

[djs45]

Hello. Can you simply duplicate template to new file and work on it ?
app.activeDocument.duplicate()

Or is it for Add layers from PSD template to a non empty PSD ?