You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: hints.rb
    path of file: ./repos/picky/server/lib/picky/index
    
    the code of the file until where you have to start completion: module Picky
  class Index
    
    class Hints
   
    
      def check hints
        hints.each do |hint|
          unless @@allowed_hints.include?(hint)
            raise <<-ERROR
              Picky cannot optimize for #{hint}.
              Allowed hints are:
                #{@@allowed_hints.join("\n")}
            ERROR
          end
        end