def assign(self, context):
    timestamp = context.timestamp
    start = timestamp - (timestamp - self.offset) % self.period
    return [IntervalWindow(Timestamp.of(s), Timestamp.of(s) + self.size)
            for s in range(start, start - self.size, -self.period)]
dataset/ETHPy150Open GoogleCloudPlatform/DataflowPythonSDK/google/cloud/dataflow/transforms/window.py/SlidingWindows.assign/original