# File lib/active_support/callbacks.rb, line 99
      def |(chain)
        if chain.is_a?(CallbackChain)
          chain.each { |callback| self | callback }
        else
          if (found_callback = find(chain)) && (index = index(chain))
            self[index] = chain
          else
            self << chain
          end
        end
        self
      end