Changed the data type of grid so that strings could be added to the n…

…umpy array without throwing an error. Increased the dimensions of grid since pieces could be moved one step beyond its previous boundaries.

tutorials/CustomEnvironment/tutorial3_action_masking.py

@@ -193,7 +193,7 @@ def step(self, actions):
 
     def render(self):
         """Renders the environment."""
-        grid = np.zeros((7, 7))
+        grid = np.zeros((8, 8), dtype=object)
         grid[self.prisoner_y, self.prisoner_x] = "P"
         grid[self.guard_y, self.guard_x] = "G"
         grid[self.escape_y, self.escape_x] = "E"