Hi - I'm new to writing Chimera code; I've started poking around in the sample scripts and the modules but and I find it a bit slow to find my way around. For example I would like to perform some simple calculations on the coordinates of a set of selected atoms, and I see many functions that take a "sel" argument, but I can't seem to find documentation on exactly what that argument is expected to contain, or the function that would return such a selection list (is it even a list) of objects. I'm sure if I spend more time, through trial and error and dir() and grep, I'll eventually figure it out, but I wonder if there isn't a more principled approach - a document on the big picture of how the code is structured, and/or a searchable list of all functions? What's the best strategy to start reading and coding Chimera scripts? Thanks! Boris