<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def walkable(self, x, y):
 """ check, if the tile is inside grid and if it is set as walkable """

        return self.inside(x, y) and self.nodes[y][x].walkable