def validate_kwargs(func, kwargs):
    """Validate arguments to be supplied to func."""
    func_name = func.__name__
    argspec = inspect.getargspec(func)
    all_args = argspec.args[:]
    defaults = list(argspec.defaults or [])

    # ignore implicit 'self' argument
    if inspect.ismethod(func) and all_args[:1] == ['self']:
        all_args[:1] = []

    # don't require arguments that have defaults
    if defaults:
        required = all_args[:-len(defaults)]
    else:
        required = all_args[:]

    # translate 'foo_' to avoid reserved names like 'id'
    trans = {
        arg: arg.endswith('_') and arg[:-1] or arg
        for arg
        in all_args
    }
    for key in list(kwargs):
        key_adj = '%s_' % key
        if key_adj in all_args:
            kwargs[key_adj] = kwargs.pop(key)

    # figure out what we're missing
    supplied = sorted(kwargs)
    missing = [
        trans.get(arg, arg) for arg in required
        if arg not in supplied
    ]
    if missing:
        raise MeteorError(
            400,
            func.err,
            'Missing required arguments to %s: %s' % (
                func_name,
                ' '.join(missing),
            ),
        )

    # figure out what is extra
    extra = [
        arg for arg in supplied
        if arg not in all_args
    ]
    if extra:
        raise MeteorError(
            400,
            func.err,
            (func_name, ' '.join(extra)) % 'Unknown arguments to %s: %s',
        )
dataset/ETHPy150Open django-ddp/django-ddp/dddp/websocket.py/validate_kwargs/swapped operands of `%`