import re


def __clean_sponsored_by_override(sponsored_by_override):
    """
    Return an empty string for 'sponsored_by_override' if the value in AdZerk is set to "blank" or "empty".
    @type sponsored_by_override: str
    """
    return re.sub(r'^(blank|empty)$', '', sponsored_by_override.strip(), flags=re.IGNORECASE)