instance method default_serializer

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 225
        def default_serializer
          if Cache.format_version == 6.1
            ActiveSupport.deprecator.warn <<~EOM
              Support for `config.active_support.cache_format_version = 6.1` has been deprecated and will be removed in Rails 7.2.

              Check the Rails upgrade guide at https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#new-activesupport-cache-serialization-format
              for more information on how to upgrade.
            EOM
            Cache::SerializerWithFallback[:passthrough]
          else
            super
          end
        end