Anonymous variables should always force create

[wouterwln]

No description provided.

[bvdmitri]

@model function ssm(n, y)
    x_0 ~ Normal(μ = 0, σ = 1.0)
    
    x_prev = x_0
    
    local x
    for i in 1:n
        x[i] ~ Normal(μ = x_prev + 1, σ = 1.0)
        x_prev = x[i]
    end
    
    y ~ Normal(μ = x[end], σ = 1.0)
end

n = 3
model = GraphPPL.create_model()
ctx = GraphPPL.getcontext(model)

y = GraphPPL.getorcreate!(model, ctx, :y, nothing);

GraphPPL.make_node!(model, ctx, ssm, y, (n = n, ), )

GraphPlot.gplot(model)