Django design patterns - models with ForeignKey references to multiple classes
what about having a generic foreign key on Assets?
I'm working through the design of a Django inventory tracking application, and have hit a snag in the model layout. I have a list of inventoried objects (Assets), which can either exist in a Warehouse or in a Shipment. I want to store different lists of attributes for the two types of locations, e.g.:

For Warehouses, I want to store the address, manager, etc.
For Shipments, I want to store the carrier, tracking number, etc.

Since each Warehouse and Shipment can contain multiple Assets, but each Asset can only be in one place at a time, adding a ForeignKey relationship to the Asset model seems like the way to go. However, since Warehouse and Shipment objects have different data models, I'm not certain how to best do this.
One obvious (and somewhat ugly) solution is to create a Location model which includes all of the Shipment and Warehouse attributes and an is_warehouse Boolean attribute, but this strikes me as a bit of a kludge.  Are there any cleaner approaches to solving this sort of problem (Or are there any non-Django Python libraries which might be better suited to the problem?)