# File lib/active_support/vendor/i18n-0.4.1/i18n/backend/flatten.rb, line 18
      def self.normalize_flat_keys(locale, key, scope, separator)
        keys = [scope, key].flatten.compact
        separator ||= I18n.default_separator

        if separator != FLATTEN_SEPARATOR
          keys.map! do |k|
            k.to_s.tr("#{FLATTEN_SEPARATOR}#{separator}",
              "#{SEPARATOR_ESCAPE_CHAR}#{FLATTEN_SEPARATOR}")
          end
        end

        keys.join(".")
      end