Function blend_open_edge 

pub fn blend_open_edge(
    solid: &BrepSolid,
    edge_id: u64,
    radius: f64,
    chamfer: bool,
    name: Option<&str>,
) -> Result<BrepSolid, String>

General OPEN-edge rolling-ball fillet or chamfer: §4.9 march + §6.9 surgery with transverse edges on the two end faces.