old_contents: import sys
  
  from kivy.lang import Builder
  from kivy.metrics import dp
  from kivy.properties import *
  from kivy.uix.boxlayout import BoxLayout
  
  #KV Lang files
  from pkg_resources import resource_filename
  path = resource_filename( __name__, 'form.kv' )
  Builder.load_file( path )
  
  
  class Form( BoxLayout ) :
      '''
      Very simple class to manage you're app views.
      Use it as if it were an Android's Activity or and iOS's View Controller.
      '''
  
      shared_navigation_controller = ObjectProperty( None )
      '''
      Navigation controller instance, used to pop\push views.
      MUST be provided.
      '''
  
      title = StringProperty( '' )
      '''
      Title provided in the navigation bar.
      '''
  
      background_color = ListProperty( None )
      '''
      Solid background color, same color as the navigation controller by default
      '''
      
      def __init__( self, **kargs ) :
          if 'shared_navigation_controller' not in kargs.keys() :
              raise ValueError( 'You MUST provide a valid controller for shared_navigation_controller' )
  
          if 'background_color' not in kargs.keys() :
              kargs['background_color'] = kargs['shared_navigation_controller'].background_color
  
          super( Form, self ).__init__( **kargs )
  
      def push( self ) :
          '''
          Will push this form to the navigation controller.
          '''
          self.shared_navigation_controller.push( self, title=self.title )
  
      def pop( self ) :
          '''
          Will pop\dismiss this form.
          '''
          self.shared_navigation_controller.push()
  
      def on_push( self, controller ) :
          '''
          Called by navigation controller whenever the form is being pushed.
          '''
          pass
  
      def on_pop( self, controller ) :
          '''
          Called by navigation controller whenever the form is being popped.
          '''
          pass
  
  
new_contents: import sys
  
  from kivy.lang import Builder
  from kivy.metrics import dp
  from kivy.properties import *
  from kivy.uix.boxlayout import BoxLayout
  
  #KV Lang files
  from pkg_resources import resource_filename
  path = resource_filename( __name__, 'form.kv' )
  Builder.load_file( path )
  
  
  class Form( BoxLayout ) :
      '''
      Very simple class to manage you're app views.
      Use it as if it were an Android's Activity or and iOS's View Controller.
      '''
  
      shared_navigation_controller = ObjectProperty( None )
      '''
      Navigation controller instance, used to pop\push views.
      MUST be provided.
      '''
  
      title = StringProperty( '' )
      '''
      Title provided in the navigation bar.
      '''
  
      background_color = ListProperty( None )
      '''
      Solid background color, same color as the navigation controller by default
      '''
      
      def __init__( self, **kargs ) :
          if 'shared_navigation_controller' not in kargs.keys() :
              raise ValueError( 'You MUST provide a valid controller for shared_navigation_controller' )
  
          if 'background_color' not in kargs.keys() :
              kargs['background_color'] = kargs['shared_navigation_controller'].background_color
  
          super( Form, self ).__init__( **kargs )
  
      def push( self ) :
          '''
          Will push this form to the navigation controller.
          '''
          self.shared_navigation_controller.push( self, title=self.title )
  
      def pop( self ) :
          '''
          Will pop\dismiss this form.
          '''
          self.shared_navigation_controller.pop()
  
      def on_push( self, controller ) :
          '''
          Called by navigation controller whenever the form is being pushed.
          '''
          pass
  
      def on_pop( self, controller ) :
          '''
          Called by navigation controller whenever the form is being popped.
          '''
          pass
  
  
subject: Fix pop from throwing an error