digraph
  G { label="MDFA of (aa|bb)*(ab(aa|bb)*ab(aa|bb)*|ba(aa|bb)*ab(aa|bb)*|ab(aa|bb)*ba(aa|bb)*|ba(aa|bb)*ba(aa|bb)*)*";
 
rankdir=LR
start[shape =none]
start ->node_1
node_1 [label="M1", shape = doublecircle]
node_1 -> node_2 [label ="b"]
node_1 -> node_4 [label ="a"]
node_2 [label="M2", shape = circle]
node_2 -> node_1 [label ="b"]
node_2 -> node_3 [label ="a"]
node_3 [label="M3", shape = circle]
node_3 -> node_4 [label ="b"]
node_3 -> node_2 [label ="a"]
node_4 [label="M4", shape = circle]
node_4 -> node_3 [label ="b"]
node_4 -> node_1 [label ="a"]
}