strict graph example { //"example" is the name of the graph
// Between the braces is a list of edges, one per line
a -- b [label="2"] // 'a -- b' means there's an
                   // undirected edge between nodes a and b
a -- c [label="3"] // '[label="3"]' on this line specifies that
                   // the edge from a to c be labelled with "3"
                   // The labels are used to show the edge weights
                   // in this graph.  
b -- c [label="1"]
c -- d [label="12"]
c -- e [label="2"]
b -- f [label="3"]
b -- e [label="6"]
e -- d [label="1"]
e -- g [label="2"]
f -- g [label="1"]
}