Constant GRID_OPEN

pub const GRID_OPEN: Grid;

A special Grid with no internal walls

use core_pb::grid::standard_grid::GRID_OPEN;
use core_pb::grid::Grid;
use core_pb::grid::computed_grid::ComputedGrid;

let grid: Grid = GRID_OPEN;
let computed_grid: ComputedGrid = grid.try_into().unwrap();