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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 isScreenOn(self):
 """ Checks if the screen is ON. @return: True if the device screen is ON """


        self.__checkTransport()
        screenOnRE = re.compile('mScreenOnFully=(true|false)')
        m = screenOnRE.search(self.shell('dumpsys window policy'))
        if m:
            return m.group(1) == 'true'
        raise RuntimeError("Couldn't determine screen ON state")