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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 File Set
        Descriptor.

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

        rec = struct.pack(self.FMT, b'\x00' * 16,
                          self.recording_date.record(), 3, 3, 1, 1,
                          self.file_set_num, 0, self.log_vol_char_set,
                          self.log_vol_ident, self.file_set_char_set,
                          self.file_set_ident, self.copyright_file_ident,
                          self.abstract_file_ident, self.root_dir_icb.record(),
                          self.domain_ident.record(), b'\x00' * 16,
                          b'\x00' * 48)[16:]
        return self.desc_tag.record(rec) + rec