def METHOD_NAME(self, item):
    """
    Select the clicked item if it is a slicing plane.
    :param GLGraphicsItem item: the item so check and select
    """
    for axis, plane in enumerate((self._x, self._y, self._z)):
        if item is plane:
            r, g, b, a = qcolor2rgbacomponents(item.color())
            item.setColor([r / 2, g / 2, b / 2, a])
            item.update()
            self._selection = item
            self._selected_axis = axis
            return