@Override
	public String toString() {
		return "Graph:  nodes=#" + nodes.size() + "  links=#" + links.size() + "\n" + nodes + "\n" + links;
	}
Represents a Graph that Flo will display. A graph consists of simple nodes and links.

@author Andy Clement
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/job/dsl/Graph.java