def update(bulk = false)
      caught = catch(:halt)  do
        if self.new?
          save(bulk)
        else
          _run_update_callbacks do
            _run_save_callbacks do
              save_without_callbacks(bulk)
            end
          end
        end
      end
    end
def update(bulk = false)
      caught = catch(:halt)  do
        if self.new?
          save(bulk)
        else
          _run_update_callbacks do
            _run_save_callbacks do
              save_without_callbacks(bulk)
            end
          end
        end
      end
    end
Trigger the callbacks (before, after, around)
 only if the document isn't new