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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _ReformatMessageString(self, message_string):
 """Reformats the message string. Args: message_string (str):
 message string. Returns: str: message string in Python format() (PEP 3101) style. """

    def _PlaceHolderSpecifierReplacer(match_object):
      """Replaces message string place holders into Python format() style."""
      expanded_groups = []
      for group in match_object.groups():
        try:
          place_holder_number = int(group, 10) - 1
          expanded_group = '{{{0:d}:s}}'.format(place_holder_number)
        except ValueError:
          expanded_group = group

        expanded_groups.append(expanded_group)

      return ''.join(expanded_groups)

    if not message_string:
      return None

    message_string = self._WHITE_SPACE_SPECIFIER_RE.sub(r'', message_string)
    message_string = self._TEXT_SPECIFIER_RE.sub(r'\\\1', message_string)
    message_string = self._CURLY_BRACKETS.sub(r'\1\1', message_string)
    return self._PLACE_HOLDER_SPECIFIER_RE.sub(
        _PlaceHolderSpecifierReplacer, message_string)