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: system_notification_creator.rb
    path of file: ./repos/i-diario/app/services
    
    the code of the file until where you have to start completion: class SystemNotificationCreator
  def self.create!(attributes)
    new(attributes).creat
    
  def create!
    users = attributes.delete(:users)
    attributes[:generic] ||= false

    raise "Users can't be blank" if users.blank?
    raise "Source can't be blank" if attributes[:source].blank? && !attributes[:generic]

    ActiveRecord::Base.transaction do
      notification = SystemNotification.create!(attributes)

      users.each do |user|
        notification.targets.find_or_create_by!(user: user)
      end

      notification
    end
  end