How do I get the orientation from a open3d.geometry.OrientedBoundingBox?

I've created a Oriented Bounding Box from a clustered sub point cloud of a Velodyne Lidar (rotating laser sensor). I want to get the orientation of the Bounding Box (preferable as a quaternion).

subpcd_o3d = o3d.utility.Vector3dVector(np.array(subpcd))o3d_bbox = o3d.geometry.OrientedBoundingBox.create_from_points(subpcd_o3d)

The Documentation has no such method: http://www.open3d.org/docs/latest/python_api/open3d.geometry.OrientedBoundingBox.html

This is confusing. Why is there apparently no orientation of the oriented bounding box?