How to use built in Voronoi in C++?

There is a Voronoi lib built in the UE4. It uses voro++ under the hood.

/Engine/Source/Runtime/Experimental/Voronoi/Public/Voronoi/Voronoi.h

And there is the struct FVoronoiCellInfo.

Documentation says that it is “All the info you would typically want about a single cell in the Voronoi diagram”, but I dont understand what does the Neighbors member of the struct means. It’s some kind of random numbers in there (positive and negative) wich does not make any sense for me :frowning:

All I need to know is what is the index of the neighbor of the current cell in the result array of cells from FVoronoiDiagram::ComputeCells(). But how can I use that random numbers? What does negative numbers means?

Somebody, help me, please!