def filter_localization_probability(df, threshold=0.75):
    """
    Remove rows with a localization probability below 0.75

    Return a ``DataFrame`` where the rows with a value < `threshold` (default 0.75) in column 'Localization prob' are removed.
    Filters data to remove poorly localized peptides (non Class-I by default).

    :param df: Pandas ``DataFrame``
    :param threshold: Cut-off below which rows are discarded (default 0.75)
    :return: Pandas ``DataFrame``
    """
    df = df.copy()
    localization_probability_mask = df['Localization prob'].values >= threshold
    return df.iloc[localization_probability_mask, :]