candidate cluster的用法和样例：
例句
- Ordinarily, the candidate set for a call includes only member functions or nonmember functions but not both.
一般而言，函数调用的候选集只包括成员函数或非成员函数，不会两者都包括。 - For a given query, we filter the whole graph through the index to get a smaller candidate set.Thus, high time-complexity subgraph isomorphism matching operations are reduced.
对于给定的查询，我们使用这些索引过滤图数据库，得到较小的候选集，减少需要进行的高时间复杂度的子图同构匹配。
