def METHOD_NAME(http_methods: HttpMethod | Method | Sequence[HttpMethod | Method]) -> set[Method]:
    """Normalize HTTP method(s) into a set of upper-case method names.
    Args:
        http_methods: A value for http method.
    Returns:
        A normalized set of http methods.
    """
    output: set[str] = set()
    if isinstance(http_methods, str):
        http_methods = [http_methods]  # pyright: ignore
    for method in http_methods:
        method_name = method.value.upper() if isinstance(method, HttpMethod) else method.upper()
        if method_name not in HTTP_METHOD_NAMES:
            raise ValidationException(f"Invalid HTTP method: {method_name}")
        output.add(method_name)
    return cast("set[Method]", output)