如何从.kv文件添加在.py文件中制作的Kivy下拉菜单？

<MyDropdown>:
    Button:
        text: 'Select an option'
        on_release: root.open_dropdown()

    DropDown:
        id: dropdown
        on_select: root.select_option(self, args[1])

        Button:
            text: 'Option 1'
            size_hint_y: None
            height: '48dp'
            on_release: dropdown.select('Option 1')

        Button:
            text: 'Option 2'
            size_hint_y: None
            height: '48dp'
            on_release: dropdown.select('Option 2')

        Button:
            text: 'Option 3'
            size_hint_y: None
            height: '48dp'
            on_release: dropdown.select('Option 3')

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.lang import Builder

Builder.load_file('path/to/your.kv')

class MyDropdown(Widget):
    def open_dropdown(self):
        self.ids.dropdown.open(self)

    def select_option(self, dropdown, option):
        print('Selected option:', option)
        dropdown.dismiss()

class MyApp(App):
    def build(self):
        return MyDropdown()

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