Add UIImagePickerController to a kivy-ios-app (Python)

Question

I want to access my images/photo gallery on an iOS device from a kivy application. Kivy has no native way implemented to do this, so I'm trying to solve it with kivy/pyobjus where I can use the UIImagePickerController (from Apples UIKit).

from kivy.app import App
from kivy.lang import Builder
from pyobjus import autoclass, protocol



class TestApp(App):

    ui = Builder.load_file("main.kv")
    def build(self):
        return self.ui

    def imagePicker(self):
        UIImagePickerController = autoclass('UIImagePickerController')
        self.picker = UIImagePickerController.alloc().init()
        self.picker.delegate = self
        self.picker.sourceType = 0

        @protocol('UIImagePickerControllerDelegate')
        def imagePickerControllerDidFinish(self, image):
           print("ABC")

The ui is just a button, which calls the imagePicker function. I have three questions on this code:

1. How can I display the imagePicker?

2. When I'm using imagePicker.delegate = self, the App crashes because

   [...] delegate, but there is no @protocol methods declared.

   But I declared a protocol with "@protocol('UIImagePickerControllerDelegate')" So why it won't use my declared protocol? (I tried also to add the "UIImagePickerControllerDelegate" in the protocols.py from pyobjus. This didn't solved the problem)

3. If the protocol will work, it is the correct way to use the "imagePickerControllerDidFinish(self, image)" method to access the image?