Redmine

I want to program this functionatity and I think is adding the code in this redmine model (app/models/user.rb) writ something like this

  # Utility method to help check if a user should be notified about an
  # event.
  #
  # TODO: only supports Issue events currently
  def notify_about?(object)
    case mail_notification
    when 'all'
      if  object.is_a?(Issue) 
           if object.allowed_statuses? 
             true
           else
             false
           end
      else
         false
      end.....

But the method allowed_statuses don't exist, could you help me ???