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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 close_dut(self, use_prepare=True):
 """ Close connection to dut. :param use_prepare: Boolean, default is True. Call prepare_connection_close before closing connection. :return: Nothing """

        if not self.stopped:
            self.logger.debug("Close '%s' connection" % self.dut_name, extra={'type': '<->'})
            if use_prepare:
                try:
                    self.prepare_connection_close()
                except TestStepFail:
                    # We can ignore this for dead Duts, just continue with cleanup
                    pass
            self.stopped = True
            Dut._dutlist.remove(self)
            # Remove myself from signalled dut list, if I'm still there
            if Dut._signalled_duts and Dut._signalled_duts.count(self):
                try:
                    Dut._signalled_duts.remove(self)
                except ValueError:
                    pass

            try:
                if not Dut._dutlist:
                    Dut._run = False
                    Dut._sem.release()
                    Dut._th.join()
                    del Dut._th
                    Dut._th = None
            except AttributeError:
                pass