def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
async def handler(client, request):
		if request.path == "/v6/challenge":
			assert request.encode().decode() == CHALLENGE_REQUEST
			response = http.HTTPResponse(200)
			response.json = {
				"challenge": "vaNgVZZH7gUse0y3t8Cksuln-TAVtvBmcD-ow59qp0E=",
				"data": "dlL7ZBNSLmYo1hUlKYZiUA=="
			}
			return response
		else:
			assert request.encode().decode() == TOKEN_REQUEST
			response = http.HTTPResponse(200)
			response.json = {
				"device_auth_token": "device token"
			}
			return response