reset_callbacks

# File activesupport/lib/active_support/callbacks.rb, line 716
        def reset_callbacks(name)
          callbacks = get_callbacks name

          ActiveSupport::DescendantsTracker.descendants(self).each do |target|
            chain = target.get_callbacks(name).dup
            callbacks.each { |c| chain.delete(c) }
            target.set_callbacks name, chain
          end

          set_callbacks(name, callbacks.dup.clear)
        end