digraph g {

	s0 [shape="circle" label="0"];
	s1 [shape="circle" label="1"];
	s2 [shape="circle" label="2"];
	s3 [shape="circle" label="3"];
	s0 -> s1 [modality="MUST" contract="NONE" label="a" group="-1"];
	s0 -> s0 [modality="MUST" color="8" contract="RED" colorscheme="reds9" label="d" group="1"];
	s1 -> s2 [modality="MUST" color="7" contract="GREEN" colorscheme="greens9" label="b" group="0"];
	s2 -> s3 [modality="MUST" contract="NONE" label="c" group="-1"];
	s3 -> s0 [modality="MUST" color="7" contract="GREEN" colorscheme="greens9" label="d" group="0"];

__start0 [label="" shape="none" width="0" height="0"];
__start0 -> s0;

}
