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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def events(self):
 """ All events in calendar within specified time range """

        if self._events is None:
            self._events = self.parent.calendar.events(
                calendarId="primary", singleEvents=True, orderBy="startTime",
                timeMin=self.since, timeMax=self.until)
        return self._events