Kivy 异常：未知类

Question

运行我的代码似乎以异常错误结束，我已经尝试了很长时间来调试它，但我无法做到

main.py

from kivy.animation import Animation
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen, ScreenManager, FadeTransition
from gpshelper import GpsHelper
import plyer

class Manager(ScreenManager):
    pass



class SelectionScreen(Screen):
    def on_start(self):
        GpsHelper().run()


class Game(Screen):
    pass


class GpsBlinker():
    def blink(self):
        anim = Animation(opacity=0, blink_size=50)
        anim.bind(on_complete=self.reset)
        anim.start(self)

    def reset(self, *args):
        self.opacity = 1
        self.blink_size = self.default_blink_size
        self.blink()


kv = Builder.load_file("hiby.kv")

class HeIsBehindYou(App):
    def build(self):
        return kv

if __name__ == '__main__':
    HeIsBehindYou().run()

main.kv

#:import FadeTransition kivy.uix.screenmanager.FadeTransition

Manager:
    transition: FadeTransition()

    SelectionScreen:
        name:'selectionscreen'
    Game:
        name:'game'


<GpsBlinker>
    default_blink_size: 25
    blink_size: 25

    canvas.before:
        Color:
            rgba: 0.5, 0.5, 0.5, 1
        RoundedRectangle:
            radius:[root.blink_size/2.0, ]
            size: [root.blink_size, root.blink_size]
            pos: root.pos[0] + root.size[0]/2.0 - root.blink_size/2.0, root.pos[1] + root.size[1]/2.0 - root.blink_size/2.0



<SelectionScreen>
    BoxLayout:
        Image:
            source: 'placeholder.png'
            size: self.texture_size
        Button:
            text: 'Start Day 1'
            on_release:
                app.root.current = "game"
                root.manager.transition.direction = "up"
                print("inside")
                root.on_start()

<Game>
    id: game
    BoxLayout:
        orientation: 'vertical'
        Image:
            source: 'digital-grid-background.jpg'
            size: self.texture_size
            size_hint: 1, 3
        GpsBlinker:
            id: blinker

运行此代码后，我收到以下错误：

raise FactoryException('Unknown class <%s>' % name)
 kivy.factory.FactoryException: Unknown class <GpsBlinker

我尝试制作一个 GPS 模块来覆盖 game(screen) 中的动画。即使我在 main.py 文件中定义了它，我仍然收到此错误