初始化方法中无法调用类变量？ [关闭]

Question

所以

DEFAULT_BRUSH_SIZE

被定义为类变量，如下所示：

class Grid:
    DEFAULT_BRUSH_SIZE = 2

然而，当我将

brush_size

设置为

DEFAULT_BRUSH_SIZE

时，正如橙色说明的最后一行所说，我收到错误消息“DEFAULT_BRUSH_SIZE is not defined.”

def __init__(self, draw_style, x, y) -> None:
    """
    Initialise the grid object.
    - draw_style:
        The style with which colours will be drawn.
        Should be one of DRAW_STYLE_OPTIONS
        This draw style determines the LayerStore used on each grid square.
    - x, y: The dimensions of the grid.

    Should also intialise the brush size to the DEFAULT provided as a class variable.
    """
    brush_size = DEFAULT_BRUSH_SIZE

不过，grid类中不是已经设置为2了吗？我做错了什么？