<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _Members(self, group):
 """Unify members of a group and accounts with the group as primary gid."""

    group.members = set(group.members).union(self.gids.get(group.gid, []))
    return group