This is the error I received after submission

[Eleena_Boppuri]

Failed test case: train_mnist’s return value has incorrect type.
Expected:
<class ‘keras.callbacks.History’>,
but got:
<class ‘tuple’>.

[balaji.ambresh]

You are returning a tuple instead of the history object which is returned from model.fit .
If you have something like history = model.fit(...), , keep in mind that a trailing comma will make the return value a tuple.