I have a long script, but the key point is here:
result = confusion_matrix(y_test, ypred)
where y_test is
    >>> y_test
    ZFFYZTN     3
    ZDDKDTY     0
    ZTYKTYKD    0
    ZYNDQNDK    1
    ZYZQNKQN    3
               ..
    ZYMDDTM     3
    ZYLNYFLM    0
    ZTNTKDY     0
    ZYYLZNKM    3
    ZYZMQTZT    0
Name: BT, Length: 91, dtype: object
and the values are
>>> y_test.values
array([3, 0, 0, 1, 3, 0, 0, 1, 0, 3, 1, 0, 3, 1, 0, 0, 3, 0, 3, 0, 0, 0,
       1, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 2, 3, 3, 0, 0, 3, 3, 1, 1, 0, 2,
       0, 0, 0, 3, 3, 3, 1, 0, 3, 3, 3, 2, 3, 3, 0, 1, 0, 3, 3, 0, 0, 0,
       0, 0, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 3, 2, 0, 0, 0, 3, 3, 3, 0,
       0, 3, 0], dtype=object)
and ypred is
>>> ypred
array([3, 0, 0, 1, 3, 0, 0, 1, 0, 3, 1, 0, 3, 1, 0, 0, 3, 0, 3, 0, 0, 0,
       1, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 2, 3, 3, 0, 0, 3, 3, 1, 1, 0, 2,
       0, 0, 0, 3, 3, 3, 1, 0, 3, 3, 3, 2, 3, 3, 0, 1, 0, 3, 3, 0, 0, 0,
       0, 0, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 3, 2, 0, 0, 0, 3, 3, 3, 0,
       0, 3, 0])
gives
    raise ValueError("Classification metrics can't handle a mix of {0} "
ValueError: Classification metrics can't handle a mix of unknown and multiclass targets
The confusing part is that I don't see any unknown targets.
so I checked out ValueError: Classification metrics can't handle a mix of unknown and binary targets but the solution there doesn't apply in my case, because all values are integers.
I've also checked Skitlearn MLPClassifier ValueError: Can't handle mix of multiclass and multilabel-indicator but there aren't any encodings in my data.
What can I do to get the confusion matrix and avoid these errors?