@startuml
'figure 1: inheritance diagram'
skinparam monochrome true
skinparam handwritten false
skinparam shadowing false
hide class circle
skinparam classAttributeIconSize 0

class Object {
+ __init__()
}

class Contact {
+ __init__()
}

class AddressHolder {
+ __init__()
}

class Friend {
+ __init__()
}

Object <|-- Contact
Object <|-- AddressHolder
Contact <|-- Friend
AddressHolder <|-- Friend

@enduml
