def expand_border(tokens, name, base_url):
    """Expand the ``border`` shorthand property.

    See https://www.w3.org/TR/CSS21/box.html#propdef-border

    """
    for suffix in ('-top', '-right', '-bottom', '-left'):
        for new_prop in expand_border_side(tokens, name + suffix, base_url):
            yield new_prop
Expand the ``border`` shorthand property.

See https://www.w3.org/TR/CSS21/box.html#propdef-border
weasyprint/css/validation/expanders.py