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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def supply_backend(optional: Union[callable, bool]=False, index_exists: bool=True):
 """ Decorator to pass the initialized backend to the decorated callable. \ Used by command line entries. If the backend cannot be created, return 1. :param optional: Either a decorated function or a value which indicates whether we should \ construct the backend object if it does not exist in the wrapped function's \ `args`: `True` means we shouldn't. :param index_exists: Whether the Git model index exists on the remote side or not. """

    real_optional = False if callable(optional) else optional

    def supply_backend_inner(func):
        @wraps(func)
        def wrapped_supply_backend(args):
            log = logging.getLogger(func.__name__)
            if real_optional and not getattr(args, "backend", False):
                backend = None
            else:
                try:
                    git_index = GitIndex(remote=args.index_repo, username=args.username,
                                         password=args.password, cache=args.cache,
                                         exists=index_exists, signoff=args.signoff,
                                         log_level=args.log_level)
                except ValueError:
                    return 1
                backend = create_backend_noexc(log, args.backend, git_index, args.args)
                if backend is None:
                    return 1
            return func(args, backend, log)
        return wrapped_supply_backend
    if callable(optional):
        return supply_backend_inner(optional)
    return supply_backend_inner