Parameters
- geometry
- Specifies the input geometry.
Return Value
      The geometry that represents the boundary of the input geometry.
      For Point - returns an empty point.
      For Multipoint - returns an empty point.
      For Envelope - returns a polyline, that bounds the envelope.
      For Polyline - returns a multipoint, using OGC specification (includes path endpoints, using mod 2 rule).
      For Polygon - returns a polyline that bounds the polygon by adding all rings of the polygon to a polyline.
    
