def if_columns(x):
    """
    This function suffixes '_columns' to a dataframe (when saving it as a file) if columns are specified and
    suffixes '_dataframe' no columns are specified (i.e. when the user wants to do EDA of the entire dataset).
    :param x: list of columns
    :return: '_columns' suffix if list of columns is provided, else '_dataframe'.
    """
    return '_columns' if len(x) != 0 else '_dataframe'