@startuml
Mediator <|- ConcreteMediator
Mediator <-- Colleague
Colleague <|-- ConcreteColleague1
Colleague <|-- ConcreteColleague2
ConcreteMediator --> ConcreteColleague1
ConcreteMediator --> ConcreteColleague2

interface Mediator
class Colleague {
  #mediator : Mediator
}

hide empty attributes
hide empty methods
@enduml