docs: def format_float_field(__, prec, number, locale):
      """Formats a fixed-point field."""
      format_ = u'0.'
      if prec is None:
          format_ += u'#' * NUMBER_DECIMAL_DIGITS
      else:
          format_ += u'0' * int(prec)
      pattern = parse_pattern(format_)
      return pattern.apply(number, locale)