Can not save ply in example. The rest works. I hadn't change any piece of code in example.

Traceback (most recent call last):
File "/pyglet_pointcloud_viewer.py", line 467, in
pyglet.app.run()
File "/usr/local/lib/python3.6/dist-packages/pyglet/app/init.py", line 138, in run
event_loop.run()
File "/usr/local/lib/python3.6/dist-packages/pyglet/app/base.py", line 142, in run
self._run()
File "/usr/local/lib/python3.6/dist-packages/pyglet/app/base.py", line 154, in _run
timeout = self.idle()
File "/usr/local/lib/python3.6/dist-packages/pyglet/app/base.py", line 275, in idle
redraw_all = self.clock.call_scheduled_functions(dt)
File "/usr/local/lib/python3.6/dist-packages/pyglet/clock.py", line 309, in call_scheduled_functions
item.func(dt, *item.args, **item.kwargs)
File "/pyglet_pointcloud_viewer.py", line 461, in run
points.export_to_ply('./out.ply', mapped_frame)
TypeError: export_to_ply(): incompatible function arguments. The following argument types are supported:
1. (self: pyrealsense2.pyrealsense2.points, arg0: str, arg1: pyrealsense2.pyrealsense2.video_frame) -> None

Invoked with: <pyrealsense2.pyrealsense2.points object at 0x7fa5240b8a08>, './out.ply', <pyrealsense2.pyrealsense2.frame object at 0x7fa5240b8c70>