Represents models that need to be fitted before forecasting.
fit the attribute to store the fitted model's object (default NA)
getFitted() returns private attribute fit
setFitted(fit_result) sets fit_result as the value of private attribute fit
setFittedFcasted(fit_function, test_randomness, fcast_function, ...) calls the fitting function, the forecasting function, performs residuals analysis and generates forecast intervals from bootstrapped residuals for ARIMA and ETS models when !super$isPiIgnored() & super$areResidualsNotNormal() & !super$areResidualsNotRandom()
executeUseModel(fit_function, fcast_function, fcast_period, ...) calls the fitting function, which uses the new training set (obtained by calling NVDModel's method getMergedTrainTestSet), then calls the forecasting function which uses generating forecasting intervals from bootstrapped residuals when !super$isBootstrapNotUsed() = TRUE