code: def reward_proximity(self):
          
          if not 'proximity' in self.mode:
              return
          mode = self.mode['proximity']
  
          # Calculate proximity reward
          reward = 0
          for sensor in self.player.sensors:
              if sensor.sensed_type == 'wall':
                  reward += sensor.proximity_norm()
              else:
                  reward += 1
  
          reward /= len(self.player.sensors)
          #reward = min(1.0, reward * 2)
          reward = min(1.0, reward * reward)
          # TODO: Configurable bonus reward threshold. Pass extra args to `__test_cond`?
          #if mode and mode and reward > 0.75 and self.__test_cond(mode):
          if mode and mode and self.__test_cond(mode):
              # Apply bonus
              reward *= mode['reward']
  
          self.player.stats['reward'] += reward
docs: Add a wall proximity reward