title: Can the Kivy language access inherited layouts and widgets?
body: <p>Can the kivy language access inherited layouts and widgets? I want to create one basic BoxLayout that contains the styling and title Label for my widget. I want to be able to inherit from this widget and add additional widgets in different positions.</p>
  
  <pre><code>from kivy.app import App
  from kivy.lang import Builder
  from kivy.uix.boxlayout import BoxLayout
  
  Builder.load_string('''
  &lt;SimpleBar&gt;:
      canvas.before:
          Color:
              rgba: 0, 0.5, 0.5, 1
          Rectangle:
              pos: self.pos
              size: self.size
      BoxLayout:
          id: my_layout
          Label:
              text: "hi"
  
  &lt;NewBar&gt;:
      Label:
          text: "2"
  ''')
  
  class SimpleBar(BoxLayout):
      def log(self, value):
          print(value)
  
  class NewBar(SimpleBar):
      def __init__(self, *args, **kwargs):
          super().__init__(*args, **kwargs)
          print(dir(self))
  
  class GeneralApp(App):
      def build(self):
          return NewBar()
  
  if __name__ == '__main__':
      GeneralApp().run()
  </code></pre>
  
  <p>Above is my basic running widget.</p>
  
  <p>I want NewBar's "2" Label to be located before SimpleBar's 'hi' Label like below.</p>
  
  <pre><code>&lt;NewBar&gt;:
       BoxLayout:
           id: my_layout
           Label:
               text: "2"
           Label:
               text: "hi"
  </code></pre>
  
  <p>I know that - can negate items. However, <code>&lt;-NewBar&gt;</code> removes all of my styling.</p>
  
  <p>Is there any way to do this in the kivy language?</p>