def METHOD_NAME(self):
    # Find works in the tested collection that have no delivery
    # mechanisms.
    titles = []
    qu = self.collection.pools_with_no_delivery_mechanisms
    qu = qu.filter(LicensePool.licenses_owned > 0)
    for lp in qu:
        edition = lp.presentation_edition
        if edition:
            title = edition.title
        else:
            title = "[title unknown]"
        identifier = lp.identifier.identifier
        titles.append(
            "%s (ID: %s)" % (title, identifier)
        )
    if titles:
        return titles
    else:
        return "All titles in this collection have delivery mechanisms."