def gap(token):
    """Validation for the ``column-gap`` and ``row-gap`` properties."""
    length = get_length(token, percentage=True, negative=False)
    if length:
        return length
    keyword = get_keyword(token)
    if keyword == 'normal':
        return keyword
Validation for the ``column-gap`` and ``row-gap`` properties.
weasyprint/css/validation/properties.py