def text_decoration_line(tokens):
    """``text-decoration-line`` property validation."""
    keywords = {get_keyword(token) for token in tokens}
    if keywords == {'none'}:
        return 'none'
    allowed_values = {'underline', 'overline', 'line-through', 'blink'}
    if len(tokens) == len(keywords) and keywords.issubset(allowed_values):
        return keywords
``text-decoration-line`` property validation.
weasyprint/css/validation/properties.py