Order of edges in FeaturedGraph

Specific Domains Machine Learning
2 
julia> using GraphSignals, Graphs

julia> N = 4
4

julia> ug = Graph(N)
{4, 0} undirected simple Int64 graph

julia> add_edge!(ug, 1, 2); add_edge!(ug, 1, 3); add_edge!(ug, 1, 4);

julia> add_edge!(ug, 2, 3); add_edge!(ug, 3, 4);

julia> fg = FeaturedGraph(ug)
FeaturedGraph:
	Undirected graph with (#V=4, #E=5) in adjacency matrix

julia> edgeidx, dst, src = collect(edges(fg))
(UInt32[0x00000001, 0x00000002, 0x00000004, 0x00000001, 0x00000003, 0x00000002, 0x00000003, 0x00000005, 0x00000004, 0x00000005], UInt32[0x00000002, 0x00000003, 0x00000004, 0x00000001, 0x00000003, 0x00000001, 0x00000002, 0x00000004, 0x00000001, 0x00000003], UInt32[0x00000001, 0x00000001, 0x00000001, 0x00000002, 0x00000002, 0x00000003, 0x00000003, 0x00000003, 0x00000004, 0x00000004])

julia> edge_index(graph(fg), 1, 2)
0x00000001

collect(edges(fg)) could collect all the index of edges and edges in pair of vertices. You can use to index edge features.
For specific edge, there is edge_index available for SparseGraph in order to get the edge index from a pair of vertex indices.