framework/resources/Datasources/identifiers/customer.json

{ "CustomerId": "100", "cityId": 10 }
{ "CustomerId": "101", "cityId": 10 }
{ "CustomerId": "102", "cityId": 10 }
{ "CustomerId": "103", "cityId": 20 }
{ "CustomerId": "104", "cityId": 30 }
{ "CustomerId": "105", "cityId": null }
{ "CustomerId": null,  "cityId": 50 }