Graphs.jl : UndefVarError: nv not defined

General Usage
1

Hi all,

I am using Jupyter Notebook on this tutorial
https://pszufe.github.io/OpenStreetMapX_Tutorial/JuliaCon2021/

I change LightGraphs into Graphs. Then there is an error when running this code:

m = get_map_data("/home/browni/LasthrimProjection/map/waghetemap.osm", use_cache=false, trim_to_connected_graph=true );

function add_graph_edge!(m::MapData, va::Int, vb::Int;symmetric=false)
    Graphs.add_edge!(m.g, va, vb)
    push!(m.e,(m.n[va], m.n[vb]) )
    symmetric && add_graph_edge!(m, vb, va; symmetric=false)
end

wI, wJ, wV = findnz(m.w) 
agent_speed = 3_000/60 # meters in minute (that  is 3km/h)
wV = wV ./ agent_speed # all distances in minutes instead of meters
points = [ENU(LLA(ttc.lat[t], ttc.lon[t]), m.bounds) for t in 1:nrow(ttc)]
nodecs = nearest_node.(Ref(m), points)

for t in 1:nrow(ttc)
    Graphs.add_vertex!(m.g)
    vx = nv(m.g)        
    push!(m.n, -vx) # add vertex to MapData - negative indices are used for special purposes
                   #for simplicity we assume no identifier clash
    m.nodes[-vx] = points[t]
    m.v[-vx] = vx
    vc = m.v[nodecs[t]]
    
    add_graph_edge!(m, vc, vx; symmetric=true)
    
    append!(wI, [vx, vc])
    append!(wJ, [vc, vx])
    append!(wV, [3.0, 3.0]) # getting in or out of TTC takes 3 minutes    
    if t>1  #build the TTC line in graph 
        add_graph_edge!(m, vx-1, vx; symmetric=false)
        append!(wI, vx-1)
        append!(wJ, vx)
        append!(wV, 2.0) # TTC travels 2 minutes between stops 
                                # this is a simplificatio of course real data
                                # could be used
        
    end
    
end
# now we construct the updated distance matrix:
m.w = sparse(wI,wJ,wV)
@assert size(m.w,1)==size(m.w,2)
@assert size(m.w,1)==nv(m.g)

The weird thing is I try on Julia REPL

using Graphs
g = path_graph(8)
nv(g)

I get the output of 8.

Why is nv becomes UndefVarError: nv not defined at JupyterNotebook?