import re


def get_source_mapping_url(css):
    """Extract the sourceMappingURL from a css string."""
    # /*# sourceMappingURL=main.scss.map */
    match = re.search(
        r'^\s*/\*# sourceMappingURL=(.*?)\s*\*/',
        css,
        flags=re.RegexFlag.MULTILINE | re.RegexFlag.IGNORECASE)
    if match:
        return match.groups()[0]
    return None