old_contents: from mapview import MapView
  from mapview.geojson import GeoJsonMapLayer
  from kivy.base import runTouchApp
  
  view = MapView()
  layer = GeoJsonMapLayer(source="https://storage.googleapis.com/maps-devrel/google.json")
  view.add_layer(layer)
  
  runTouchApp(view)
  
new_contents: from mapview import MapView
  from mapview.geojson import GeoJsonMapLayer
  from kivy.base import runTouchApp
  import sys
  
  if len(sys.argv) > 1:
      source = sys.argv[1]
  else:
      source = "https://storage.googleapis.com/maps-devrel/google.json"
  
  view = MapView()
  layer = GeoJsonMapLayer(source=source)
  view.add_layer(layer)
  
  runTouchApp(view)
  
subject: change geojson example to allow testing an external url