class Asciidoctor::Extensions::Group

inside the {Group#activate} method.
{Extensions.register} method. Extensions are registered with the Registry
invoking the {Group.register} method or passing the subclass to the
The Group should be subclassed and registered with the Registry either by
Public: A Group is used to register one or more extensions with the Registry.

def activate registry 

def activate registry
  raise ::NotImplementedError
end

def register name = nil 

def register name = nil
  Extensions.register name, self
end