Never Turned Up

A climbing gym has a list of members and a log of visits. The owner wants to email the members who joined but have never come in.

Task: write no_shows(members, visits).

• members is a dictionary of two lists, "member_id" and "name". Each member number appears once, and every name is different.
• visits is a dictionary of two lists, "member_id" and "wall", one entry per visit. There is at least one visit. A member can visit many times.
• Some visits come from member numbers that aren't in members (day passes). They don't matter here.
• Return the names of the members with no visits at all, sorted alphabetically. If every member has visited, return an empty list.