def has_token(token_sequence: str, tokens: str) -> bool:
    """Returns true, if `token` is contained in the blank-spearated
    token sequence. If `token` itself is a blank-separated sequence of
    tokens, True is returned if all tokens are contained in
    `token_sequence`::

        >>> has_token('bold italic', 'italic')
        True
        >>> has_token('bold italic', 'normal')
        False
        >>> has_token('bold italic', 'italic bold')
        True
        >>> has_token('bold italic', 'bold normal')
        False
    """
    # assert validate_token_sequence(token_sequence)
    # assert validate_token_sequence(token)
    return not tokens or set(tokens.split(' ')) <= set(token_sequence.split(' '))