```ruby
require 'sprockets/media_query_combiner/processor'

if defined?(Rails)
  module Sprockets
    module MediaQueryCombiner
      class Engine < Rails::Engine
        initializer :setup_media_query_combiner, after: 'sprockets.environment', group: :all do |app|
          app.assets.register_postprocessor 'text/css', Sprockets::MediaQueryCombiner::Processor
          app.assets.register_bundle_processor 'text/css', Sprockets::MediaQueryCombiner::Processor
        end
      end
    end
  end
end
```

Use ::Rails instead of Rails
user
```ruby
require 'sprockets/media_query_combiner/processor'

if defined?(::Rails)
  module Sprockets
    module MediaQueryCombiner
      class Engine < ::Rails::Engine
        initializer :setup_media_query_combiner, after: 'sprockets.environment', group: :all do |app|
          app.assets.register_postprocessor 'text/css', Sprockets::MediaQueryCombiner::Processor
          app.assets.register_bundle_processor 'text/css', Sprockets::MediaQueryCombiner::Processor
        end
      end
    end
  end
end
```
assistant