Why pad a_graph and b_graph to length 11?

[yippp]

I am interested in your work. While I read the code, I found that during preprocessing, in the class get_graph_features_from_smi in data_utils.py.
The codes

    # padding
    for a_graph in a_graphs:
        while len(a_graph) < 11:            # OH MY GOODNESS... Fe can be bonded to 10...
            a_graph.append(1e9)

    for b_graph in b_graphs:
        while len(b_graph) < 11:            # OH MY GOODNESS... Fe can be bonded to 10...
            b_graph.append(1e9)

I cannot understand why the atom and bond graphs needed to be padded to length 11. Could you tell me something about it?
Thanks a lot.

[zhengkaitu]

@yippp As in the comment, during our own testing with cornor cases, we found some metal complexes can literally have up to 10 bonds (e.g. for Fe centers bonded to 10 ligands). Therefore we decided to pad to 11 just to be more robust.