Help with scripting: what are the components of a facial expression?

Saving facial expressions requires an awful lot of clicking. Even if my character's head is what's selected in the scene, the dialog to save a pose preset comes up with the entire figure selected for saving each time.
To make things easier, I want to write a script that saves only the expression. So far I've got my script recursing through the skeleton's nodes to find the head. But now that my script knows where to start looking for stuff to save, what should get written out to form a working expression preset?
Comments
You should just look at an existing pose preset .duf file, or create a new one, and then use that as a template for what needs to be written.
D'oh! I shoulda thought of that.