Tutorial for maxflow.fastmin

[Cq5616]

I am trying to solve a multi-label problem using the alpha-expansion move algorithm implemented in maxflow.fastmin.aexpansion_grid(D, V, max_cycles=None, labels=None) I didn't quite understand the definitions of arrays D and V.

For instance, If i have a 5*5 grid and consider 4 labels, what should the sizes of D and V be? It would really help if you had a tutorial or an example on this function. Thank you so much!!