Inheritance/Single

class Animal {}
class Dog is Animal {}
class Cat is Animal {}
class Lab is Dog {}
class Collie is Dog {}

say Collie.^parents;     # undefined type object
say Collie.new.^parents; # instantiated object

Output:

((Dog) (Animal))
((Dog) (Animal))

The .^parents notation indicates a method call to the object's metaobject rather than to the object itself.