Local Properties are incorrectly reported as roots

[JakeGinnivan]

void Main()
{
        var engine = new DependencyEngine();
        engine.Assign(() => C).From(() => A + B, e => { });
        engine.Assign(() => D).From(() => A + C, e => { });

        engine.ToDotFormat(options: new VisualisationOptions { ShowRoot = false }).Dump();
}

public int A { get; set; }
public int B { get; set; }
public int C { get; set; }
public int D { get; set; }

Results in:

digraph  {
     __1 [label="(A + B)", fillcolor="lightblue", style="filled", shape="octagon"];
     __5 [label="(A + C)", fillcolor="lightblue", style="filled", shape="octagon"];

}

Expected:

digraph  {
     __1 [label="(A + B)", fillcolor="lightblue", style="filled", shape="octagon"];
     __2 [label="C", shape="box", style="filled,rounded"];
     __5 [label="(A + C)", fillcolor="lightblue", style="filled", shape="octagon"];
     __3 [label="A", shape="box", style="filled,rounded"];
     __4 [label="B", shape="box", style="filled,rounded"];
     __6 [label="D", shape="box", style="filled,rounded"];

    __1 -> __2;
    __2 -> __5;
    __5 -> __6;
    __3 -> __1;
    __3 -> __5;
    __4 -> __1;
}

Can get this result by setting ShowRoot to true