def parse(self, rrstr):
        # type: (bytes) -> None
        '''
        Parse a Rock Ridge Platform Dependent record out of a string.

        Parameters:
         rrstr - The string to parse the record out of.
        Returns:
         Nothing.
        '''
        if self._initialized:
            raise pycdlibexception.PyCdlibInternalError('PD record already initialized!')

        (su_len_unused, su_entry_version_unused) = struct.unpack_from('=BB', rrstr[:4], 2)

        self.padding = rrstr[4:]

        # We assume that the caller has already checked the su_entry_version,
        # so we don't bother.

        self._initialized = True
Parse a Rock Ridge Platform Dependent record out of a string.

        Parameters:
         rrstr - The string to parse the record out of.
        Returns:
         Nothing.