The contour consists of one or more ordered sets of Edge objects. A loop can enclose a void region or a region that encloses an area. An Edge object can be used by more than one Loop (maximum two). An EdgeUse object represents the use of an Edge object inside this Loop. The Loop should be thought of as directly connected to the EdgeUse object, rather than to the Edge object. The EdgeUse object then holds the topological relationship of the Edge as it pertains to a given Loop.
