rray representing classes (class_names is required)
                       4. numerical values for text regresssion (class_names should be left empty)
        x_test(list): list of training texts
        y_test(list): labels in one of the following forms:
                       1. list of integers representing classes (class_names is required)
                       2. list of strings representing classes (class_names is not needed and ignored.)
                       3. a one or multi hot encoded array rep