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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 strace_configure(self, port_width):
 """Configures the trace port width for tracing. Note that configuration cannot occur while STRACE is running. Args: self (JLink):
 the ``JLink`` instance port_width (int):
 the trace port width to use. Returns: ``None`` Raises: ValueError: if ``port_width`` is not ``1``, ``2``, or ``4``. JLinkException: on error. """

        if port_width not in [1, 2, 4]:
            raise ValueError('Invalid port width: %s' % str(port_width))

        config_string = 'PortWidth=%d' % port_width
        res = self._dll.JLINK_STRACE_Config(config_string.encode())
        if res < 0:
            raise errors.JLinkException('Failed to configure STRACE port')

        return None