instance method preserve_encoding

# File activesupport/lib/active_support/vendor/i18n-0.4.1/i18n/backend/base.rb, line 190
        def preserve_encoding(string)
          if string.respond_to?(:encoding)
            encoding = string.encoding
            result = yield
            result.force_encoding(encoding) if result.respond_to?(:force_encoding)
            result
          else
            yield
          end
        end