@startuml
'figure 2: diamond diagram'
skinparam monochrome true
skinparam handwritten false
skinparam shadowing false
hide class circle
skinparam classAttributeIconSize 0

class BaseClass {
+ call_me()
}

class LeftSubclass {
+ call_me()
}

class RightSubclass {
+ call_me()
}

class SubClass {
+ call_me()
}

BaseClass <|-- LeftSubclass
BaseClass <|-- RightSubclass
LeftSubclass <|-- SubClass
RightSubclass <|-- SubClass

@enduml
