Function: get_card_from_uid

--Usage--
> get_card_from_uid(input: "uid")

Returns the [[type:card]] with the given uid inside the set.
Returns nil if no card was found.

--Parameters--
! Parameter	Type				Description
| @input@	[[type:string]]		The uid of the card we want to retrieve.
| @set@		[[type:set]]		The set in which to look. This can be omited since 'set' is a predefined variable.