edge { arrowstyle: filled; }
graph {
  colorscheme: x11;
  flow: south;
  title: G;
}
group {
  align: center;
  fill: inherit;
}

( cluster_0
  [ aaaaaaaaaaaaaaaaaaa ]
  [ b ]
) { align: right; label: Right aligned; }

( cluster_1
  [ c ]
  [ ddddddddddddddd ]
) { align: left; label: Left aligned; }

[ aaaaaaaaaaaaaaaaaaa ] --> [ b ]
[ c ] --> [ ddddddddddddddd ]