def check_label(dataframe, accepted_labels = None):
    """
    Validate labels

    Parameters
    ----------
    dataframe : dataframe
        a dataframe that you want to check labels
    accepted_labels: either None or a list of new labels
        None: When you want to use the default labels ('PRS', 'REP', 'OTR', 'NEU')
        a list of new labels: When you want to change the labels (ex. ['OTR_academic, 'OTR_behavior])

    Returns
    -------
    dataframe
        rows of which label is not an element of the list we input
    """
    if accepted_labels == None:
        label_list = ['PRS', 'REP', 'OTR', 'NEU']
        return dataframe[~dataframe['label'].isin(label_list)]
    else:
        label_list = accepted_labels
        return dataframe[~dataframe['label'].isin(label_list)]