Can anybody explain how when using an extra lazy collection contains is suppose to work?

Specifically if you are using synthetic primary keys what is "contains" actually going to compare with or how can I get it to compare using natural key identifiers instead of synthetic ones.

In my use case the thing I want to ask if it contains has no primary key identifier at the time I make my comparison so I cannot say to my collection does it contain this thing based on it's synthetic primary key.

I want to be able to have extra lazy collection that allows me to to control how the existing check on my object is performed and one that doesn't rely on the join properties of the collection as those are all synthetic.

Make sense?