removeIfNonNeighbor method
Implementation
void removeIfNonNeighbor(Vertex? n){
if(n == null) return;
final neighbors = this.neighbors;
final faces = this.faces;
final offset = neighbors.indexOf(n);
if (offset == - 1 ) return;
for (int i = 0; i < faces.length; i ++ ) {
if(faces[i] != null && faces[i]!.hasVertex(n)) return;
}
neighbors.splice(offset, 1);
}