Undirected graph edges not adding successfully

[kenahoo]

Here's a chunk of code demonstrating what seems like a problem:

using Graphs, MetaGraphsNext

graph = MetaGraph(
    complete_graph(2),
    ["3" => nothing, "2" => nothing],
    [("3", "2") => nothing],
)

println("Has key \"2\"->\"3\"? $(haskey(graph, "2", "3"))")
# Output> Has key "2"->"3"? false

println("Has key \"3\"->\"2\"? $(haskey(graph, "3", "2"))")
# Output> Has key "3"->"2"? false

(from, to) = first(edge_labels(graph))
println("First edge: $from -> $to")
# Output> First edge: 3 -> 2

println(graph[from, to])
# ERROR: KeyError: key ("2", "3") not found
# Stacktrace:
# [1] getindex
#   @ ./dict.jl:498 [inlined]
# [2] getindex(meta_graph::MetaGraph{…}, label_1::String, label_2::String)
#   @ MetaGraphsNext ~/.julia/packages/MetaGraphsNext/Ofw3U/src/dict_utils.jl:25
# [3] top-level scope
#   @ REPL[37]:1

The graph seems to know that it should have an edge between "2" and "3", but getindex(graph, "2", "3") (and the reverse order too) fail. Is this a known problem?

A fix seems to be to sort all edge labels alphabetically in the third argument to the MetaGraph() constructor, but in my real application that's not very convenient.