def rank_features(explanation):
    """ Given an explanation of type (name, value) provide the ranked list of feature names according to importance

    Parameters
    ----------
    explanation : list

    Returns
    ----------
    List contained ranked feature names
    """

    ordered_tuples = sorted(explanation, key=lambda x : abs(x[1]), reverse=True)  
    results = [tup[0] if tup[1] != 0 else ("Nothing shown",0) for tup in ordered_tuples]
    return results