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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 highrisk_special_prefixes(self):
 """ Access the highrisk_special_prefixes :returns: twilio.rest.voice.v1.dialing_permissions.country.highrisk_special_prefix.HighriskSpecialPrefixList :rtype: twilio.rest.voice.v1.dialing_permissions.country.highrisk_special_prefix.HighriskSpecialPrefixList """

        if self._highrisk_special_prefixes is None:
            self._highrisk_special_prefixes = HighriskSpecialPrefixList(
                self._version,
                iso_code=self._solution['iso_code'],
            )
        return self._highrisk_special_prefixes