def is_unique_set(string: str) -> bool:
    """
    This function uses a set to determine the string contains unique characters
    >>> is_unique_set("train")
    True
    >>> is_unique_set("test")
    False
    """

    hash_set = set()
    for i in string:
        hash_set.add(i)
    return len(string) == len(hash_set)