def get_docs_to_commit(self):
        try:
            spec = {'synced': False}
            fields = {'_id': 0}
            cur = self.db.docs.find(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        return list(cur)
def combinationSum(self, candidates, target):
        self.result = []
        self.dfs(candidates,0,target,[])
        return self.result