Update app.py

app.py

@@ -25,7 +25,7 @@ if "models" in pathlib.Path.cwd().parts:
     os.chdir('..')
 elif not pathlib.Path('models').exists():
   os.system('git clone --depth 1 https://github.com/tensorflow/models')
-cd models/research/
+os.chdir('models/research/')
  
 from object_detection.utils import ops as utils_ops
 from object_detection.utils import label_map_util