code: def format_percent_field(__, prec, number, locale):
      
      prec = PERCENT_DECIMAL_DIGITS if prec is None else int(prec)
      locale = Locale.parse(locale)
      pattern = locale.percent_formats.get(None)
      return pattern.apply(number, locale, force_frac=(prec, prec))
docs: Formats a percent field.