cess_mode='standard'.
    maxlen(int): each document can be of most &lt;maxlen&gt; words. 0 is used as padding ID.
    ngram_range(int): size of multi-word phrases to consider
                      e.g., 2 will consider both 1-word phrases and 2-word phrases
                           limited by max_features
    val_pct(float): Proportion of training to use for validation.
                    Has no effect if val_filepath is supplied.
    preprocess_mode (str):  Either 'standard' (normal tokenization) or on