Fix for the error: AttributeError: Custom classes or functions exported with your `Learner` not available in namespace. Re-declare/import before loading: Can't get attribute 'is_cat' on <module '__main__' from '/home/user/app/app.py'>

app.py

@@ -5,6 +5,9 @@ from fastai.vision.core import PILImage
 from fastai.learner import load_learner
 import skimage
 
+# Define the is_cat function that was used when creating the model
+def is_cat(x): return x[0].isupper()  # This is a common implementation, adjust if yours was different
+
 learn = load_learner('model.pkl')
 
 labels = learn.dls.vocab