in_memory_controller_namespaces

# File actionpack/lib/action_dispatch/routing/deprecated_mapper.rb, line 21
      def in_memory_controller_namespaces
        namespaces = Set.new
        ActionController::Base.descendants.each do |klass|
          next if klass.anonymous?
          namespaces << klass.name.underscore.split('/')[0...-1].join('/')
        end
        namespaces.delete('')
        namespaces
      end