问如何将任意python文件连接到任意kivy文件？

EN

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout

class SnakeGame(FloatLayout):
    pass

class SnakeGameApp(App):
    def build(self):
        return SnakeGame()

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

#: include snake.kv

<SnakeGame>:
    Snake:
        pos: 300, 300

# Control object for the Snake view object in snake.kv

class Snake(Widget):
    def move(self):
        print("Moving")

#: import Widget kivy.uix.widget.Widget
<Snake@Widget>:
    size_hint: None, None
    size: 15, 15
    canvas:
        Color:
            rgba: 1, 0, 0, 1
        Rectangle:
            pos: self.pos
            size: self.size
    on_touch_down: self.move() # There is an error here: Snake object has
                               # no attribute move.
                               # How can i connect to the snake.py
                               # file here the same it was automatically
                               # connecting the SnakeGame class in the main.py
                               # file with the SnakeGame class in the snakegame.py file
                               # ???