Function turbine_blade 

pub fn turbine_blade() -> Program

A turbine: a blade lofted through sections on three offset datum planes, patterned six times round a revolved hub and joined to it, as drawn in the editor.

An example drawn in the editor and kept as the program it saved (in src/drawn/): its sketches as they were drawn, which no code says better. Its tests build it like every other example, so a change to the format that breaks it is found there: save it again from the editor.