get pointclout error and how to save the pointcloud

[Wooxinyu]

When I use open3d to save the pointcloud like this, error is pcl_o3d.points = o3d.utility.Vector3dVector(point_clouds)
RuntimeError

 pcl_o3d = o3d.geometry.PointCloud()
        pcl_o3d.points = o3d.utility.Vector3dVector(point_clouds)
        filename = os.path.join(save_folder, f'point_cloud_{count}.ply')
        o3d.io.write_point_cloud(filename, pcl_o3d)
        print(f"Saved {filename}")

then ,get_pointcloud will error :
points = points.reshape((-1, 3))
AttributeError: 'NoneType' object has no attribute 'reshape'
they are running different threads ,l dont konw why make this error