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: fallbacks.rb
    path of file: ./repos/brew/Library/Homebrew/vendor/bundle-standalone/ruby/2.3.0/gems/i18n-1.5.3/lib/i18n/backend
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

# I18n locale fallbacks are useful when you want your application to use
# translations from other locales when translations for the current locale are
# missing. E.g. you might want to use :en translations when translations in
# your applications main
    
      def exists?(locale, key)
        I18n.fallbacks[locale].each do |fallback|
          begin
            return true if super(fallback, key)
          rescue I18n::InvalidLocale
            # we do nothing when the locale is invalid, as this is a fallback anyways.
          end
        end

        false
      end