def get_ck_value(row, ck_frame, metric, key='class_name', verbose=False):
    """
    Returns the value for the given metric for a particular source
    :param row: the data frame row for the test
    :param ck_frame: the frame with all the ck metrics
    :param metric: the given metric
    :param key: the key for the metric

    """
    cut = row[key]

    aux = ck_frame[ck_frame['className'] == cut][metric]
    if len(aux) != 1 and verbose:
        print("\t* {} entries for {}".format(str(len(aux)), cut))
    return aux.iloc[0]