@AbhishekC1725 Data-Admin-Operator-ID has only the core operator details. If suppose you need to access pyaccessaddititonal group(all the access groups in a operator id, its a value list) of the operator record you can't get from Data-Admin-Operator-ID class. You need to do class join with Index-Operator class. Because pyaccessgroupaddititonal is not exposed so you cant write a RD and get that column, but with Index-Operator you can do class and get that because whenver a new access group is added to an operator ID, a new record will be inserted to index-operator class. 

You can verify this-> app explorer-> Index-operator-> Click on the class-> You will see many instances-> You can filter with your operator ID

Now add a access group and now again check your operator instances will be added to index-operator class.

Conclusion-> To access other properties/columns which are not exposed in Data-admin-operator-iD class you can get it through index-operator class

Also you can open index-operator class definition and check the history tab for explanation