Answering my own question: you can define attributes in the DOT language as shown below.
MT
--
[graphviz, target=graphviz-example, format=png]
....
graph ethane {
dpi=300
subgraph {
C_0 -- H_0 [type=s];
C_0 -- H_1 [type=s];
C_0 -- H_2 [type=s];
C_0 -- C_1 [type=s];
C_1 -- H_3 [type=s];
C_1 -- H_4 [type=s];
C_1 -- H_5 [type=s];
}
}
....