Returns the boundary of a line or area. The boundary of a line is a complex point geometry containing line end points. The boundary of an area is a geometry containing all the rings in the area. This will be a simple line if the area has only an outer ring, otherwise it will be a complex line.
Parameter 1 - A line or area geometry.
Parameter 2 - Boundary geometry of the ring or endpoint.
Returns: A boundary geometry of an area or line. For point geometries, a Null value is returned.
Note: This function supports 3D and 2D geometries.