def on(self, event, *handlers):  # pylint: disable=invalid-name

        def _on_wrapper(*handlers):
            """wrapper for on decorator"""
            self.events[event].extend(handlers)
            return handlers[0]

        if handlers:
            return _on_wrapper(*handlers)
        return _on_wrapper
register a handler to a specified event
dataset/ETHPy150Open timofurrer/pyobservable/observable/core.py/Observable.on