def position(token):
    """``position`` property validation."""
    if token.type == 'function' and token.name == 'running':
        if len(token.arguments) == 1 and token.arguments[0].type == 'ident':
            return ('running()', token.arguments[0].value)
    keyword = get_single_keyword([token])
    if keyword in ('static', 'relative', 'absolute', 'fixed'):
        return keyword
``position`` property validation.
weasyprint/css/validation/properties.py