def min_width_height(token):
    """``min-width`` and ``min-height`` properties validation."""
    # See https://www.w3.org/TR/css-flexbox-1/#min-size-auto
    keyword = get_keyword(token)
    if keyword == 'auto':
        return keyword
    else:
        return length_or_precentage([token])
``min-width`` and ``min-height`` properties validation.
weasyprint/css/validation/properties.py