docs: 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