Generic text captcha recognizing

At this point model can predict generic captcha (generated by captcha package) with ~89% accuracy on test set. It was trained on generated model, where every captcha consists of 4 letters, where each of those letters is upper or lower case, and labels for those captchas are case-insensitive (therefore model has 32 classes).

Note: Accuracy is computed as follows - either you guess captcha entirely (1) or you make a mistake (0).