Function map_model::make::initial::geometry::generalized_trim_back

fn generalized_trim_back(
    roads: &mut BTreeMap<OriginalRoad, Road>, 
    i: NodeID, 
    lines: &[(OriginalRoad, Pt2D, PolyLine, PolyLine)], 
    debug: Vec<(String, Polygon)>
) -> Result<(Polygon, Vec<(String, Polygon)>)>