add comment for stopping the simulation

PathPlanning/HybridAStar/a_star.py

@@ -78,6 +78,7 @@ def dp_planning(sx, sy, gx, gy, ox, oy, reso, rr):
         # show graph
         if show_animation:  # pragma: no cover
             plt.plot(current.x * reso, current.y * reso, "xc")
+            # for stopping simulation with the esc key.
             plt.gcf().canvas.mpl_connect('key_release_event',
                     lambda event: [exit(0) if event.key == 'escape' else None])
             if len(closedset.keys()) % 10 == 0: