def addSelectedDateListener(self, listener, dobj=False):
        if dobj:
            self.selectedDObjListeners.append(listener)
        else:
            self.selectedDateListeners.append(listener)
call to remove generates a DataCollectionDeleteMessage
dataset/ETHPy150Open pyjs/pyjs/pyjswidgets/pyjamas/ui/Calendar.py/DateSelectedHandler.addSelectedDateListener--crossover with--dataset/ETHPy150Open glue-viz/glue/glue/core/tests/test_data_collection.py/TestDataCollection.test_remove_broadcast