code: def _contact(self, contact, begin):
      tile = None
      obj = None
      u1 = contact.fixtureA.body.userData
      u2 = contact.fixtureB.body.userData
      if u1 and "road_friction" in u1.__dict__:
          tile = u1
          obj = u2
      if u2 and "road_friction" in u2.__dict__:
          tile = u2
          obj = u1
      if not tile:
          return
  
      # inherit tile color from env
      tile.color[:] = self.env.road_color
      if not obj or "tiles" not in obj.__dict__:
          return
      if begin:
          obj.tiles.add(tile)
          if not tile.road_visited:
              tile.road_visited = True
              self.env.reward += 1000.0 / len(self.env.track)
              self.env.tile_visited_count += 1
  
              # Lap is considered completed if enough % of the track was covered
              if (
                  tile.idx == 0
                  and self.env.tile_visited_count / len(self.env.track)
                  > self.lap_complete_percent
              ):
                  self.env.new_lap = True
      else:
          obj.tiles.remove(tile)
  
imports: import math
  from typing import Optional, Union
  import numpy
  import gym
  from gym import spaces
  from gym.envs.box2d.car_dynamics import Car
  from gym.error import DependencyNotInstalled, InvalidAction
  from gym.utils import EzPickle
label_desc: Use image node_id 4 for calling the FrictionDetector obj's underlying member method code with example usage: obj._contact(contact, begin) without return types