code: def _attempt_to_format_accrued_digits(self):
          
          for number_format in self._possible_formats:
              num_re = re.compile(number_format.pattern)
              if fullmatch(num_re, self._national_number):
                  if number_format.national_prefix_formatting_rule is None:
                      self._should_add_space_after_national_prefix = False
                  else:
                      self._should_add_space_after_national_prefix = bool(_NATIONAL_PREFIX_SEPARATORS_PATTERN.search(number_format.national_prefix_formatting_rule))
                  formatted_number = re.sub(num_re, number_format.format, self._national_number)
                  return self._append_national_number(formatted_number)
          return U_EMPTY_STRING
docs: Checks to see if there is an exact pattern match for these digits. If so, we should use this
          instead of any other formatting template whose leadingDigitsPattern also matches the input.