Added Class.getParents

lib/Class.js

@@ -162,6 +162,17 @@ class Class {
 		return { ids: ids, objs: students };
 	}
 
+	async getParents() {
+		const parentInters = await Promise.all(this.students.map(s =>
+			s.getParents()));
+
+		const parents = [];
+
+		parentInters.forEach(pi => parents.push(...pi));
+
+		return parents;
+	}
+
 	getUsers(ids, type) {
 		const types = {
 			account: 'Account',