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Context: We also looked at the EMNIST dataset provided by Cohen et al. (2017), an extended version of MNIST that extends the number of classes by introducing uppercase and lowercase characters. However, to be able to use it seamlessly one needs to not only extend the deep learning framework’s MNIST helpers, but also change the underlying deep neural network to classify these extra classes.

Question: What is the issue with EMNIST dataset?
To be able to use it seamlessly one needs to not only extend the deep learning framework’s MNIST helpers but also change the underlying deep neural network to classify these extra classes.