Function define_placed 

pub fn define_placed(
    ctx: &mut StepContext<'_>,
    name: &str,
    placed: &PlacedArgs,
    placement: Placement,
) -> GeopResult<()>

Places the part placed says — the program in its file, its parameters set to its inputs, the steps after its own run after — as the instance name, at placement (see geop_core_program::placed::place), and draws it ([draw]): again only when what it is drawn from changed. A step of the part placed that fails fails this, after it is placed and drawn as far as it builds.