You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: base.rb
    path of file: ./repos/coursemology2/app/notifiers/notifier
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
# The base class of notifiers. This is meant t
    
  def notify(recipient, notification)
    return unless notification.email?

    case recipient
    when Course
      email_course(notification)
    when User
      email_user(notification)
    else
      raise ArgumentError, 'Invalid recipient type'
    end