```ruby
module Inky
  module Rails
    class TemplateHandler
      class << self
        def engine_handler
          type = ::Inky.configuration.template_engine
          ActionView::Template.registered_template_handler(type) ||
            raise("No template handler found for #{type}")
        end

        def call(template)
          compiled_source = engine_handler.call(template)
          "Inky::Core.new.release_the_kraken(begin; #{compiled_source};end)"
        end
      end
    end
  end
end

ActiveSupport.on_load(:action_view) do
  ActionView::Template.register_template_handler :inky, Inky::Rails::TemplateHandler
end
```

Refactor to use class instead of singleton
user
```ruby
module Inky
  module Rails
    class TemplateHandler
      def initialize(compose_with = nil)
        @engine_handler = ActionView::Template.registered_template_handler(compose_with) if compose_with
      end

      def engine_handler
        return @engine_handler if @engine_handler
        type = ::Inky.configuration.template_engine
        ActionView::Template.registered_template_handler(type) ||
          raise("No template handler found for #{type}")
      end

      def call(template)
        compiled_source = engine_handler.call(template)
        "Inky::Core.new.release_the_kraken(begin; #{compiled_source};end)"
      end
    end
  end
end

ActiveSupport.on_load(:action_view) do
  ActionView::Template.register_template_handler :inky, Inky::Rails::TemplateHandler.new
end
```
assistant