Python 如何在按下按钮时将屏幕过渡更改为从右到左

我想用python代码做一个按钮go 到上一个屏幕，问题是它使用的是默认的过渡动画(从左到右)，看起来很奇怪.我在处理这个文件时没有遇到任何问题，但是在这个特定的屏幕中，我必须使用Python代码来更改该属性.我想让它从右到左，因为默认的动画看起来很奇怪.

我在KV文件中这样做:

root.manager.transition.direction = "right"个

我试过了:

back_button.on_release = lambda: setattr(self.manager, "transition", "right")，但这不是这样的:)

完整的屏幕代码:

class Contraindicaciones(MDScreen):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Scrollview
        self.scrollview_contraindicaciones = MDScrollView(size_hint=(1, None), size = (Window.width, Window.height))

        # GridLayout
        layout_contraindicaciones = MDGridLayout(orientation = "lr-tb", spacing = "60dp", padding = "20dp", size_hint_x = 1, size_hint_y = None, cols = 2)
        layout_contraindicaciones.bind(minimum_height = layout_contraindicaciones.setter("height"))

        # Go Back Button:
        invisible_label1 = MDLabel(text = "")
        invisible_label1.size_hint_y = None
        invisible_label1.size_hint_x = 0.5
        invisible_label1.height = dp(50)

        back_button_layout = MDBoxLayout(orientation = "vertical")
        back_button = MDFillRoundFlatButton(text = "Anterior", font_name = "fonts/Lato-Bolditalic.ttf")
        back_button.haling = "left"
        back_button.size_hint_y = None
        back_button.size_hint_x = 0.5

        back_button.on_release = lambda: setattr(self.manager, "transition", "right")
        back_button.on_release = lambda: setattr(self.manager, 'current', 'c_t')


        back_button_layout.add_widget(back_button)
        layout_contraindicaciones.add_widget(back_button_layout)
        layout_contraindicaciones.add_widget(invisible_label1)

        #title
        title_label = MDLabel(text = "Contraindicaciones", halign="left")
        title_label.font_size = "15dp"
        title_label.size_hint_y = None
        title_label.size_hint_x = 1
        title_label.font_name = "fonts/Lato-Bolditalic.ttf"
        title_label.height = dp(50)

        # Invisible Label
        invisible_label2 = MDLabel(text = "")
        invisible_label2.size_hint_y = None
        invisible_label2.size_hint_x = 0.25
        invisible_label2.height = dp(50)

        # Title and Invisible Label to not mess the rest up
        layout_contraindicaciones.add_widget(title_label)
        layout_contraindicaciones.add_widget(invisible_label2)

        contraindicaciones = ["Hemorragia intracraneal (HIC) previa", "Lesión vascular cerebral estructural conocida",
        "Neoplasia intracraneal maligna conocida ya sea primaria o metastásica", "Accidente cerebrovascular isquémico en un plazo de 3 meses",
        "Sospecha de disección aórtica", "Hemorragia activa o diátesis hemorrágica", "Traumatismo craneoencefálico cerrado importante o traumatismo facial en los últimos 3 meses",
        "Cirugía intracraneal o intramedular en un plazo de 3 meses", "Hipertensión no controlada grave", "En caso de estreptoquinasa, el tratamiento previo debe ser dentro de los 6 meses previos"]

        for contraindicacion in contraindicaciones:
            size_checkbox = dp(32)
            size_labels = dp(12)
            checkbox = MDCheckbox(size_hint = (0.5, None), size = (size_checkbox, size_checkbox))
            label = MDLabel(text = contraindicacion, size_hint = (0.5, None), size = (size_labels, size_labels))
            label.font_name = "fonts/Lato-Italic.ttf"
            layout_contraindicaciones.add_widget(label)
            layout_contraindicaciones.add_widget(checkbox)

        # Button and invisible label
        invisible_label3 = MDLabel(text = "")
        invisible_label3.size_hint_y = None
        invisible_label3.size_hint_x = 0.5
        invisible_label3.height = dp(50)

        next_button = MDFillRoundFlatButton(text = "Continuar", font_name = "fonts/Lato-Bolditalic.ttf")
        next_button.haling = "right"
        next_button.size_hint_y = None
        next_button.size_hint_x = 0.5
        next_button.on_release = lambda: setattr(self.manager, 'current', 't_y')

        layout_contraindicaciones.add_widget(invisible_label3)
        layout_contraindicaciones.add_widget(next_button)

        #Se agrega Grid a Scroll
        self.scrollview_contraindicaciones.add_widget(layout_contraindicaciones)
        self.add_widget(self.scrollview_contraindicaciones)

以下是屏幕管理器和应用程序的代码:

class WindowManager(MDScreenManager):
    pass

class PatricApp(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.previous_screen = ""
    def build(self):
        Window.clearcolor = (255,255,255,255)
        self.root_widget = Builder.load_file("patric.kv")
        return self.root_widget
    def show_time_picker(self):
        time_dialog = MDTimePicker()
        time_dialog.open()

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