el
                  - 'linreg' for linear regression using embedding layers
                  - 'bigru' for Bidirectional GRU with pretrained word vectors
                  - 'bert' for BERT Text Classification
                  - 'distilbert' for Hugging Face DistilBert model

    train_data (tuple): a tuple of numpy.ndarrays: (x_train, y_train)
    preproc: a ktrain.text.TextPreprocessor instance.
             As of v0.8.0, this is required.
    metrics(list): metrics to use
    verbose (boolean): verbos