/**
* Only check edges for which there were duplicates, since these are
* the only ones which might be the result of dimensional collapses.
*/
if (!depth.isNull()) {
depth.normalize();
for (int i = 0; i < 2; i++) {
if (!lbl.isNull(i) && lbl.isArea() && !depth.isNull(i)) {
/**
* if the depths are equal, this edge is the result of
* the dimensional collapse of two or more edges. It has