class
Classnames to attach to the node, edge, graph, or cluster's SVG element
type: string, default: ""
Combine with stylesheet for styling SVG output
using CSS classnames.
Multiple space-separated classes are supported.
See also:
Example:
digraph G {
  graph [class="cats"];
  subgraph cluster_big {
    graph [class="big_cats"];
    "Lion" [class="yellow social"];
    "Snow Leopard" [class="white solitary"];
  }
}- Edges
 - Nodes
 - Clusters
 - Graphs
 
Note: svg only.