如何返回MongoDB中存在的数组中的重复元素(忽略大小写)？输入(MongoDB中的文档){"userID":"USER001","userName":"manish","collegeIDs":["COL_HARY","COL_MARY","COL_JOHNS","COL_CAS","COL_JAMES","col_mary","COL_JOHNS","COL_JOHNS"]}预期输出:{"collegeIDs":["COL_MARY","col_mary","COL_JOHNS"]}注意:只检查内容，不检查大小写。返回列表中的所有可能性我尝试过的db.myList.aggrega