is not possible to edit parsed file

i have parsed three model file with data as key in response which returned as Datum class in parsed model , so am trying to use those three files in one page but return error which say Datum class is available in file A ,B and C .
I have tried to solve by importing parsed model class as prefix but data not parsed .

serviceModel.Services;
roomModel.Rooms;
StoreModel.Stores;

_services = serviceModel.servicesFromJson(response.body);
_room = roomModel.roomsFromJson(response.body);
_stores = storeModel.storesFromJson(response.body);

but both _services, _room,_store return nulls