def escape_control_chars!(string)
      string.gsub!(CONTROL_CHARACTERS) do |character|
        UTF8Encoding::REPLACEMENT_SCHEME[character]
      end
      string
    end
def escape_control_chars!(string)
      string.gsub!(CONTROL_CHARACTERS) do |character|
        UTF8Encoding::REPLACEMENT_SCHEME[character]
      end
      string
    end
Escapes in-place any control characters in `string`, before returning it.