Function slippy_map_tiles::size_bbox_zoom_metatiles

pub fn size_bbox_zoom_metatiles(
    bbox: &BBox, 
    zoom: u8, 
    metatile_scale: u8
) -> Option<usize>

How many metatiles, of this scale, does this bbox cover at this zoom If there is an overflow for usize, None is returned, if not, a Some(...) This is less likely to overflow than size_bbox_zoom because metatiles are larger