add TODO comment

Signed-off-by: kyoichi-sugahara <kyoichi.sugahara@tier4.jp>

Author: kyoichi-sugahara

planning/behavior_path_start_planner_module/src/shift_pull_out.cpp

@@ -100,6 +100,12 @@ std::optional<PullOutPath> ShiftPullOut::plan(const Pose & start_pose, const Pos
     shift_path.points = cropped_path.points;
 
     // check lane departure
+    // The method for lane departure checking verifies if the footprint of each point on the path is
+    // contained within a lanelet using `boost::geometry::within`, which incurs a high computational
+    // cost.
+    // TODO(someone): improve the method for detecting lane departures without using
+    // lanelet::ConstLanelets, making it unnecessary to retain departure_check_lanes_ as a member
+    // variable.
     if (
       parameters_.check_shift_path_lane_departure &&
       lane_departure_checker_->checkPathWillLeaveLane(