__str__ on Params incorrect

[taeold]

Moved back to back log - change breaks a few things so internals needs a bit of a refactor. This bug is also present on JS Functions implementation

[taeold]

I can use params if I manually type "{{ params.COLLECTION }}" into my reference path, but not if I use f"{collection_param}". Maybe the str method is broken?

[kevinthecheung]

#76 related?