# Group (i.e. subgraph) + Group. OK.
(cluster_1: [Solar system] -> {arrowhead: diamond} [Earth]) {bgcolor: cornflowerblue; label: Locale}
(cluster_2: [Great] -> {arrowhead: odot} [Small]) {bgcolor: lightblue; label: Creatures}
# Group (i.e. subgraph) + Group. OK.
(cluster_1: [Solar system] -> {arrowhead: diamond} [Earth]) {bgcolor: cornflowerblue; label: Locale}
(cluster_2: [Great] -> {arrowhead: odot} [Small]) {bgcolor: lightblue; label: Creatures}