def define_event(name, args = {})
      args = {:create_method => true}.merge(args)
      name = name.to_sym
      
      if args[:create_method]
        define_method name do
          return event(name)
        end
      end
      
      @unobservable_instance_events ||= Set.new
      if @unobservable_instance_events.include? name
        return false
      else
        @unobservable_instance_events.add name
        return true
      end
    end
def define_event(name, args = {})
      args = {:create_method => true}.merge(args)
      name = name.to_sym
      
      if args[:create_method]
        define_method name do
          return event(name)
        end
      end
      
      @unobservable_instance_events ||= Set.new
      if @unobservable_instance_events.include? name
        return false
      else
        @unobservable_instance_events.add name
        return true
      end
    end
Returns true if the instance event is defined.
 Returns false otherwise.