:param s1:  A list or string
    :param s2:  Another list or string
    :returns:    The levenshtein distance between the two

def _levenshtein_distance(s1, s2):
    """
    :param s1:  A list or string
    :param s2:  Another list or string
    :returns:    The levenshtein distance between the two
    """
    if len(s1) > len(s2):
        s1, s2 = s2, s1
    distances = range(len(s1) + 1)
    for index2, num2 in enumerate(s2):
        new_distances = [index2 + 1]
        for index1, num1 in enumerate(s1):
            if num1 == num2:
                new_distances.append(distances[index1])
            else:
                new_distances.append(1 + min((distances[index1],
                                             distances[index1+1],
                                             new_distances[-1])))
        distances = new_distances
    return distances[-1]