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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 watchpoint_info(self, handle=0, index=-1):
 """Returns information about the specified watchpoint. Note: Either ``handle`` or ``index`` can be specified. If the ``index`` is not provided, the ``handle`` must be set, and vice-versa. If both ``index`` and ``handle`` are provided, the ``index`` overrides the provided ``handle``. Args: self (JLink):
 the ``JLink`` instance handle (int):
 optional handle of a valid watchpoint. index (int):
 optional index of a watchpoint. Returns: An instance of ``JLinkWatchpointInfo`` specifying information about the watchpoint if the watchpoint was found, otherwise ``None``. Raises: JLinkException: on error. ValueError: if both handle and index are invalid. """

        if index < 0 and handle == 0:
            raise ValueError('Handle must be provided if index is not set.')

        wp = structs.JLinkWatchpointInfo()
        res = self._dll.JLINKARM_GetWPInfoEx(index, ctypes.byref(wp))
        if res < 0:
            raise errors.JLinkException('Failed to get watchpoint info.')

        for i in range(res):
            res = self._dll.JLINKARM_GetWPInfoEx(i, ctypes.byref(wp))
            if res < 0:
                raise errors.JLinkException('Failed to get watchpoint info.')
            elif wp.Handle == handle or wp.WPUnit == index:
                return wp

        return None