one_way_junction单行线路口

单行线路口是指该路口的所有road均为单行线，比如一个普通的十字路口由8条road组成.

• 用途：创建junction城区路口的静态场景（地图）
• 参数：参数如下表.

  Parameter	Type	Mandatory	Description
  lane_num	int	yes	单方向车道数量.
  bikeway	bool	yes	是否有自行车道.
  sidewalk	bool	yes	是否有人行道.
  junction_type	junction_type	yes	路口的类型，目前支持两种类型crossroad（十字路口）和T-junction（丁字路口）

• 参数取值范围：

lane_num: int = [1, 2, 3, 4]
bikeway: bool = [true, false]
sidewalk: bool = [true, false]
junction_type: junction_type = ["crossroad", "T-junction"]

my_junction_type: junction_type = "crossroad"
my_junction: one_way_junction with:
    keep(it.lane_num == 2)
    keep(it.bikeway == false)
    keep(it.sidewalk == false)
    keep(it.junction_type == my_junction_type)