private void _sealBorders(Dictionary<ExitDirection, bool> necessaryBorders)
{
if (!necessaryBorders.ContainsKey(ExitDirection.North)) necessaryBorders.Add(ExitDirection.North, false);
if (!necessaryBorders.ContainsKey(ExitDirection.East)) necessaryBorders.Add(ExitDirection.East, false);
if (!necessaryBorders.ContainsKey(ExitDirection.South)) necessaryBorders.Add(ExitDirection.South, false);
if (!necessaryBorders.ContainsKey(ExitDirection.West)) necessaryBorders.Add(ExitDirection.West, false);
if (!necessaryBorders.ContainsKey(ExitDirection.Up)) necessaryBorders.Add(ExitDirection.Up, false);
if (!necessaryBorders.ContainsKey(ExitDirection.Down)) necessaryBorders.Add(ExitDirection.Down, false);
}