add all_neighbor_labels function

[apriljunge]

In Graphs.jl the all_neighbors function returns in- and outneighbors for all graphs. This is especially needed for directed graphs. (Docs).

I think it would be nice to have a corresponding function like all_neighbor_labels in this package. Implementation should be straight forward like in Graphs.jl.

What do you think?

[gdalle]

I think we already do have it!
https://juliagraphs.org/MetaGraphsNext.jl/dev/api/#MetaGraphsNext.neighbor_labels-Tuple{MetaGraph,%20Any}

[apriljunge]

This only works für undirected Graphs. For directed graphs neighbor_labels just returns labels of out neighbors. This is expected behaviour, because it relies on Graphs.neighbors. From the docomentation of Graphs.jl for Graphs.neighbors:

For directed graphs, the default is equivalent to outneighbors; use all_neighbors to list inbound and outbound neighbors.

This is why I think all_neighbor_labels is still needed to get in- and outbound neighbors on directed graphs.

[gdalle]

Oh right, sorry I missed that. Feel free to open a PR adding it then!

[gdalle]

Closed by #77