def callback(self, value):
        for subscr in self._itersubscriptions():
            subscr.callback(value)
Ensure the end points exists and are consisent with the javascript range
dataset/ETHPy150Open ClusterHQ/flocker/flocker/restapi/testtools.py/EventChannel.callback--crossover with--dataset/ETHPy150Open pyjs/pyjs/pyjswidgets/pyjamas/selection/Range.py/Range.ensureEndPoints