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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 getVersionNumber(self):
 """get OpenThreadWpan stack firmware version number"""

        print '%s call getVersionNumber' % self.port
        versionStr = self.__sendCommand(WPANCTL_CMD + 'getprop -v NCP:Version')[0]

        return self.__stripValue(versionStr)