Как в KivyMD получить значение c поля для ввода MDTextField?

Я использую kivymd. Как я могу получить значение из MDTextField с id: summ, при нажатии на кнопку с id: bt2. Я создал функцию def show, которая должна принять это самое значение, и попытался реализовать ее работу, но что-то не получется(

выдает такую ошибку:

File "F:\Fin_app\layouts.kv", line 46, in <module>
     on_press: app.show(self)
 TypeError: MainApp.show() takes 1 positional argument but 2 were given

main.py

from kivy.lang import Builder
from kivy.properties import StringProperty, BooleanProperty

from kivymd.uix.boxlayout import MDBoxLayout
from kivymd.uix.screen import MDScreen
from kivymd.app import MDApp
from kivymd.theming import ThemableBehavior

Builder.load_file('layouts.kv')
Builder.load_file('backdrop.kv')
class ExampleBackdrop(MDScreen):

    pass


class ItemBackdropBackLayer(ThemableBehavior, MDBoxLayout):
    icon = StringProperty("android")
    text = StringProperty()
    selected_item = BooleanProperty(False)

    def on_touch_down(self, touch):
        if self.collide_point(touch.x, touch.y):
            for item in self.parent.children:
                if item.selected_item:
                    item.selected_item = False
            self.selected_item = True
        return super().on_touch_down(touch)


class MainApp(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.title = "KivyMD Example - Backdrop"
        self.theme_cls.primary_palette = "DeepPurple"

    def show(self, **kwargs):
        print(self.root.ids.summ.text)

    def build(self):
        self.root = ExampleBackdrop()


if __name__ == "__main__":
    MainApp().run()

backdrop.kv

<ExampleBackdrop>

    MDBackdrop:
        id: backdrop
        left_action_items: [['menu', lambda x: self.open()]]
        title: "Example Backdrop"
        radius_left: "25dp"
        radius_right: "25dp"
        header_text: "Меню:"

        MDBackdropBackLayer:
            MyyBackdropBackLayer:
                id: backlayer

        MDBackdropFrontLayer:
            MyyBackdropFrontLayer:
                backdrop: backdrop

layouts.kv

#:import os os
#:import Window kivy.core.window.Window
#:import IconLeftWidget kivymd.uix.list.IconLeftWidget
#:import images_path kivymd.images_path


<ItemBackdropFrontLayer@TwoLineAvatarListItem>
    icon: "android"

    IconLeftWidget:
        icon: root.icon


<MyyBackdropFrontLayer@ScrollView>
    backdrop: None
    backlayer: None

    MDGridLayout:
        adaptive_height: True
        cols: 2
        padding: "5dp"

        ItemBackdropFrontLayer:
            text: "Кнопка 1"
            icon: "monitor-star"
            on_press:
                root.backdrop.open(-Window.height / 2)

        MDTextField:
            id: NotUsed
            hint_text: "Вводи сюда"



<MyyBackdropBackLayer@ScrollView>
    MDGridLayout:
        adaptive_height: True
        cols: 2
        padding: "5dp"

        ItemBackdropFrontLayer:
            id: bt2
            text: "кнопка 2"
            secondary_text: "с действием"
            icon: "monitor-star"
            on_press: app.show(self)

        MDTextField:
            id: summ
            hint_text: "Вводи сюда"
            mode: "fill"