title: Unexpected TypeError while calling ScreenManager.get_screen() function
body: <p>I am trying to use get_screen() function to get a screen with the name given in a form of string. Annoyingly, though, I keep on getting a </p>
  
  <pre><code> TypeError: 'kivy.properties.ListProperty' object is not iterable
  </code></pre>
  
  <p>error. I have no idea what I am doing wrong. Here's an MRE:</p>
  
  <pre><code>from kivy.app import App
  from kivy.uix.screenmanager import Screen, ScreenManager
  from kivy.lang import Builder
  
  class WindowManager(ScreenManager):
      pass
  
  class Screen_One(Screen):
      def button(self):
          return WindowManager.get_screen(WindowManager,'Two')
  
  class Screen_Two(Screen):
      pass
  
  class Application(App):
      def build(self):
          return design
  
  if __name__ == '__main__':
      with open('design.txt', encoding='utf-8') as f:
          design = f.read()
      design = Builder.load_string(design)
      Application().run()
  </code></pre>
  
  <p>...and the kv...</p>
  
  <pre><code>WindowManager:
      Screen_One:
      Screen_Two:
  
  &lt;Screen_One&gt;:
      name: 'One'
      Button:
          size_hint: (0.2, 0.2)
          on_release:
              root.button()
  
  &lt;Screen_Two&gt;:
      name: 'Two'
  </code></pre>
  
  <p>Edit: I tried changing the code on assumption that get_screen() function works with the class names of screens, and not actual screen names defined in kv. Still nothing.</p>