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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 record(self):
        # type: () -> bytes
        '''
        A method to generate the string representing this UDF Partition Volume
        Descriptor.

        Parameters:
         None.
        Returns:
         A string representing this UDF Partition Volume Descriptor.
        '''
        if not self._initialized:
            raise pycdlibexception.PyCdlibInternalError('UDF Partition Volume Descriptor not initialized')

        rec = struct.pack(self.FMT, b'\x00' * 16,
                          self.vol_desc_seqnum, self.part_flags,
                          self.part_num, self.part_contents.record(),
                          self.part_contents_use.record(), self.access_type,
                          self.part_start_location, self.part_length,
                          self.impl_ident.record(), self.implementation_use,
                          b'\x00' * 156)[16:]
        return self.desc_tag.record(rec) + rec