digraph identifier {
	node [shape = circle, height = 0.6, fontname = "monospace", fixedsize = true, fontsize = 12];
    edge [fontname = "monospace", fontsize = 12];

    node [shape = circle];
    START;

    node [style = filled];
    ID;

    START -> ID [label = "[_a-zA-Z]"];
    ID -> ID [label = "[_0-9a-zA-Z]"];
    
}