Nicholas Tolley

@jasmainak I've removed the `__get_item__()` functionality as I think it added a lot of complexity that was until now, mostly untested and documented.

@rythorpe @jasmainak @katduecker this is ready to go! The main goal was to remove the overly complicated cell_response indexing functionality

@gtdang this is a pretty small PR that was supposed to be merged but was forgotten when things were stalled with the unit tests failing It'd be good to have...