老师你好，在新目标人教版九年级英语P116页中有这样一个句子“Robert is just one young overseas Chinese who has come to visit his ancestors’ homeland, as part of the In Search of Roots summer camp program关于句中“as part of the In Search of Roots summer camp program” 我们老师说它是作“has come to visit his ancestors’ ” 的同位语，可学生不理解老师的解释，因为我从来没见过同位语可以这样用.我认为有两种理解
1. “as part of the In Search of Roots summer camp program”做Robert 的同位语，意思是Robert作为这个夏令营的一员
2.作某种状语，修饰 “has come to visit his ancestors’ homeland”，意思是参观祖先的故乡是活动的一部分.
不知道我的理解是否正确？麻烦老师分析一下“as part of the In Search of Roots summer camp program”到底是什么结构，谢谢！