---------------------------------------------------------------------
:NOTES:
---------------------------------------------------------------------
 
purely functional means we don't have to reinstantiate Engine each time, 
and IMHO there's no need even without big changes.

We can do something like this:

	sub collapse_object {
		my $self = shift;
		my %storage;
		$self->map_attributes(sub { $self->collapse_attribute(\%storage, @_) });
	}

or we can make collapse_attribute return KVPs (I think that's nicer and more reusable):

	sub collapse_object {
		my $self = shift;
        return {
			$self->map_attributes('collapse_attribute'),
			__class__ => $self->object->meta->name,
		};
    }

I 100% agree, the instantiation of Engine was actually a leftover from an 
early version, so I can make this more functional without too much trouble.

---------------------------------------------------------------------

I am not going to do this quite yet, I think there might actually still be value to 
keeping it the way it is. I want to attempt an engine extension first, before i do this.