def prepare_data(data, features=('gpm', 'tbc', 'epm', 'aht')):
    """
    Preparing data: splitting it on features/targets.
    :param data: pd.DataFrame with column 'label' contains labels for data points
    :param features: wanted features to use in classification
    :return: Features data frame and targets series
                (pd.DataFrame, pd.Series)
    """
    features = data[list(features)]
    targets = data['label']
    return features, targets