def in6_iseui64(x):
    """
    Return True if provided address has an interface identifier part
    created in modified EUI-64 format (meaning it matches *::*:*ff:fe*:*).
    Otherwise, False is returned. Address must be passed in printable
    format.
    """
    eui64 = inet_pton(socket.AF_INET6, '::ff:fe00:0')
    x = in6_and(inet_pton(socket.AF_INET6, x), eui64)
    return x == eui64