Convert communication namedtuple to this class.

        Args:
            pub (obj): :class:`.Archive` instance which will be converted.

        Returns:
            obj: :class:`DBArchive` instance.

def from_comm(cls, pub):
        '''
        Convert communication namedtuple to this class.

        Args:
            pub (obj): :class:`.Archive` instance which will be converted.

        Returns:
            obj: :class:`DBArchive` instance.
        '''
        filename = None
        if pub.b64_data:
            filename = cls._save_to_unique_filename(pub)

        return cls(
            isbn=pub.isbn,
            uuid=pub.uuid,
            aleph_id=pub.aleph_id,

            dir_pointer=filename
        )