def METHOD_NAME(self, df):
    '''Transform a DataFrame such that it contains the predictions of the LightGBMModel
    in form of a virtual column.
    :param df: A vaex DataFrame.
    :return copy: A shallow copy of the DataFrame that includes the LightGBMModel prediction as a virtual column.
    :rtype: DataFrame
    '''
    copy = df.copy()
    lazy_function = copy.add_function('lightgbm_prediction_function', self, unique=True)
    expression = lazy_function(*self.features)
    copy.add_virtual_column(self.prediction_name, expression, unique=False)
    return copy