    # File 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