How to extract holes in alpha_shape_2d result?

[nimafo]

I am looking for a way to extract distinct subsets of the alpha_shape2d which represent closed boundaries in the alpha_shape. So I want to be able to access each hole(or closed boundary) separately in the following alpha_shape_result:

I implemented an algorithm to start with an edge and find the next connected alpha-segments until all the alpha-segments are met. This assumes for each alpha-segments there are exactly two edges connected to it. This is a wrong assumption, given that there can be more than 2 indicent alpha-segments for each vertex.
example from the above mesh:

Do you have any suggestion for doing this?