import unicodedata


def transliterate(string):
    """
    Replace non-ASCII characters with an ASCII approximation. If no
    approximation exists, the non-ASCII character is ignored. The string must
    be ``unicode``.

    Examples::

        >>> transliterate('älämölö')
        'alamolo'
        >>> transliterate('Ærøskøbing')
        'rskbing'

    """
    normalized = unicodedata.normalize('NFKD', string)
    return normalized.encode('ascii', 'ignore').decode('ascii')