UsersViewModel.kt

class UsersViewModel : ViewModel() {
    
    private val usersSnapLiveData: LiveData<Resource<DataSnapshot>> by lazy { 
        UsersSnapLiveData() 
    }
 
    val usersLiveData: LiveData<Resource<HashMap<String, User>>> by lazy {
        usersSnapLiveData.mapLiveDataResource<
                DataSnapshot,                  // from
                HashMap<String, User>          // to
        >(DataSnapshot::getTypedValue)         // transformation function
    }
    
}