 
 extension Edge: Statement {
     func serialize(with context: Graph) -> String {
-        return "\(from.identifier) \(context.type.op.rawValue) \(to.identifier)"
+        return "\(from.identifier) \(context.type.edgeOperator) \(to.identifier)"
     }
 }
 

        case undirected = "graph"
        case directed = "digraph"

        var op: Edge.Operator {
            switch self {
            case .undirected: return .undirected
            case .directed: return .directed
            }
        }
    }

}

struct Edge {
    var from: Node
    var to: Node
}
