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)
def setSSS(self, lenp3, lenp1, lenp2):
        self.lenp3 = lenp3
        self.lenp1 = lenp1
        self.lenp2 = lenp2
        self.ap1 = math.acos(((self.lenp2 * self.lenp2 + self.lenp3 * self.lenp3) - self.lenp1 * self.lenp1) / (2* self.lenp2 * self.lenp3))
        self.ap2 = math.acos(((self.lenp1 * self.lenp1 + self.lenp3 * self.lenp3) - self.lenp2 * self.lenp2) / (2* self.lenp1 * self.lenp3))
        self.ap3 = math.acos(((self.lenp1 * self.lenp1 + self.lenp2 * self.lenp2) - self.lenp3 * self.lenp3) / (2* self.lenp1 * self.lenp2))