Step 3 - De-Embedding Routine
To create the desired polarity we need to:
Unionization is required since it is not possible to sort out whether one boundary contains another if they actually touch or overlap.
A boundary that is not surrounded by any other boundary has an embedding level = 0. A boundary that is surrounded by only one boundary has an embedding level of 1. The surrounding boundary is called the parent and the first level of surrounded boundaries are called the parent's children.