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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 licenses(self):
 """Returns a string of the built-in licenses the J-Link has. Args: self (JLink):
 the ``JLink`` instance Returns: String of the contents of the built-in licenses the J-Link has. """

        buf_size = self.MAX_BUF_SIZE
        buf = (ctypes.c_char * buf_size)()
        res = self._dll.JLINK_GetAvailableLicense(buf, buf_size)
        if res < 0:
            raise errors.JLinkException(res)
        return ctypes.string_at(buf).decode()