instance method instantiate_observers

# File activerecord/lib/active_record/observer.rb, line 34
      def instantiate_observers
        return if @observers.blank?
        @observers.each do |observer|
          if observer.respond_to?(:to_sym) # Symbol or String
            observer.to_s.camelize.constantize.instance
          elsif observer.respond_to?(:instance)
            observer.instance
          else
            raise ArgumentError, "#{observer} must be a lowercase, underscored class name (or an instance of the class itself) responding to the instance method. Example: Person.observers = :big_brother # calls BigBrother.instance"
          end
        end
      end