def is_unsupported_size_mechanism_type(size_mechanism: str) -> bool:
    """Whether the given size mechanism is unknown/unsupported."""
    return size_mechanism not in {
        "fixed",
        "len",
        "len-in-bytes",
        "ivi-dance",
        "passed-in",
        "passed-in-by-ptr",
        "ivi-dance-with-a-twist",
        "two-dimension",
        "custom-code",
    }