def update(self, data):
        """
        C_DigestUpdate

        :param data: data to add to the digest
        :type data: bytes or string
        """
        data1 = ckbytelist(data)
        rv = self._lib.C_DigestUpdate(self._session, data1)
        if rv != CKR_OK:
            raise PyKCS11Error(rv)
        return self
C_DigestUpdate

        :param data: data to add to the digest
        :type data: bytes or string