polyop.getOpenEdges <Poly poly>Bits in the result bitarray are set if the corresponding edge is open (used by only 1 ace).
polyop.getBorderFromEdge <Poly poly> <int edge>Bits in the result bitarray are set for open edges in the poly that are connected using open edges to the specified edge.
All one-sided edges in polys can be grouped into chains, end to end, which represent boundaries of the poly. For instance, in a box with one side deleted, all the one-sided edges are part of the chain that goes around the hole. If the specified edge is not open, the resulting bitarray is empty.