'Return the serial number of a Revoked structure
:return: The serial number as a string'

def get_serial(self):

    bio = _new_mem_buf()
    result = _lib.i2a_ASN1_INTEGER(bio, self._revoked.serialNumber)
    if (result < 0):
        _raise_current_error()
    return _bio_to_string(bio)
