change DEFINE_list to DEFINE_string.
change DEFINE_list to DEFINE_string.

jiaphuan/models,tombstone/models,derekjchow/models,jiaphuan/models,derekjchow/models,tombstone/models,jiaphuan/models,cshallue/models,derekjchow/models,jiaphuan/models,tombstone/models,cshallue/models,jiaphuan/models,jiaphuan/models,derekjchow/models,alexgorban/models,tombstone/models,tombstone/models,cshallue/models,alexgorban/models,derekjchow/models,cshallue/models,tombstone/models,alexgorban/models,cshallue/models,alexgorban/models,alexgorban/models