def fillNaToMode(data):
    """Iterates through NA values and changes them to the mode

    Parameters:
    dataset (pd.Dataset): Both datasets

    Returns:
    data (pd.Dataset) : Dataset with any NA values in the columns listed changed to the mode

   """
    columns = ["MSZoning", "Functional", "Electrical", "KitchenQual", "Exterior1st", "Exterior2nd"]
    for column in columns:
        data[column] = data[column].fillna(data[column].mode()[0])
    return data