Constructing a Tree Tensor Network Operator doesn't work on integer labelled vertices

[JoeyT1994]

The following code:

using ITensors
using ITensorNetworks
using NamedGraphs
using Graphs

n =2
g = NamedGraph(path_graph(n))
s = siteinds("S=1/2", g)

ops = OpSum()
ops += 1.0, "Sz", 1, "Sz", 2

@show TTN(ops, s)

produces the error:

Which goes away if one names the vertices of g as tuples instead of Integers.

Is this unexpected? Or is TTN() only defined for IndexNetworks labelled with tuples?

[mtfishman]

I noticed this issue as well, it should be fixed by ITensor/DataGraphs.jl#15.