BinaryInput

def __init__(self, *args: Any, **kwargs: Any) -> None:
    # MRO walk: map positional args and collect defaults.
    positional_names: list[str] = []
    defaults: dict[str, Any] = {}
    seen: set[str] = set()

    for klass in reversed(type(self).__mro__):
        for name, f in getattr(klass, "_event_fields_", {}).items():
            if name not in seen:
                if not f.kw_only:
                    positional_names.append(name)
                if name not in kwargs:
                    default = f.get_default()
                    if default is not Ellipsis:
                        defaults[name] = default
            seen.add(name)

    if args:
        if len(args) > len(positional_names):
            raise TypeError(
                f"{type(self).__name__}() takes {len(positional_names)} "
                f"positional argument(s) but {len(args)} were given"
            )
        for name, value in zip(positional_names, args):
            if name in kwargs:
                raise TypeError(f"{type(self).__name__}() got multiple values for argument '{name}'")
            kwargs[name] = value
            defaults.pop(name, None)

    # Apply defaults first, then user-provided kwargs so that
    # property setters (e.g. content -> _content) aren't overwritten
    # by a field default applied afterwards.
    for key, value in defaults.items():
        setattr(self, key, value)
    for key, value in kwargs.items():
        setattr(self, key, value)