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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 calculate_statistics(self, start, stop):
 """Starts the statistics calculation. :param start: The left limit of the time window in percent. :param stop: The right limit of the time window in percent. .. note:: The calculation takes some time. Check the status byte to see when the operation is done. A running scan will be paused until the operation is complete. .. warning:: The SR850 will generate an error if the active display trace is not stored when the command is executed. """

        cmd = 'STAT', Integer, Integer
        self._write(cmd, start, stop)