set the timeout limit.

        :Parameters:
            #. timeout (number): The maximum delay or time allowed to successfully set the
               lock. When timeout is exhausted before successfully setting the lock,
               the lock ends up not acquired.

def set_timeout(self, timeout):
        """
        set the timeout limit.

        :Parameters:
            #. timeout (number): The maximum delay or time allowed to successfully set the
               lock. When timeout is exhausted before successfully setting the lock,
               the lock ends up not acquired.
        """
        try:
            timeout = float(timeout)
            assert timeout>=0
            assert timeout>=self.__wait
        except:
            raise Exception('timeout must be a positive number bigger than wait')
        self.__timeout  = timeout