Short Example.ts

const fooMembers = new Set([1,2]);
const barMembers = new Set([1,3]);

const groups: Map<Set<number>, String> = new Map();
groups.set(fooMembers,"foo");
groups.set(barMembers,"bar");

console.log(groups.get(fooMembers));
console.log(groups.get(new Set([1,2])));

TypescriptPain.ts

type MemberId = number;
type GroupMembers = Set<MemberId>;
type GroupsByMembers = Map<GroupMembers, String>;

const fooMembers: GroupMembers = new Set([1,2]);
const barMembers: GroupMembers = new Set([1,3]);

const groups: GroupsByMembers = new Map();
groups.set(fooMembers,"foo");
groups.set(barMembers,"bar");

console.log(groups.get(fooMembers));
// "foo"
console.log(groups.get(new Set([1,2])));
// undefined

see Playground Link