a family of maps的用法和样例：
- A family of maps was defined and then it was used to characterize the structure of GV-semigroups so that the latter was further clearly recognized.
- One flat can accommodate a family of five.
- Each apartment could house a family of six.
- It costs quite a lot to clothe a family of six .
- It costs quite a lot to clothe a family of six.
- A family of parallel lines cut the conic.