digraph gaspump {
        rankdir=LR;
        node [shape = circle;];
        edge [color = grey; fontsize=10];
        S0 -> S1 [ label = "Lift Nozzle" ]
        S1 -> S0 [ label = "Replace Nozzle" ]
        S1 -> S2 [ label = "Authorize Pump" ]
        S2 -> S0 [ label = "Replace Nozzle" ]
        S2 -> S3 [ label = "Pull Trigger" ]
        S3 -> S2 [ label = "Release Trigger" ]
}