 for preprocess_mode=&#39;standard&#39;.
        maxlen (int):  maximum length of tokens in document
        ngram_range (int):  If &gt; 1, will include 2=bigrams, 3=trigrams and bigrams
        train_test_names (list):  list of strings represnting the subfolder
                                 name for train and validation sets
                                 if test name is missing, &lt;val_pct&gt; of training
                                 will be used for validation
        preprocess_mode (str):  Ei