Get the record string type value given the record_type.

def _get_record(self, record_type):
        """Get the record string type value given the record_type."""
        if not self.has_record_type(record_type):
            raise errors.Unsupported()
        if str(record_type) not in self._records:
            raise errors.Unimplemented()
        return self._records[str(record_type)]