def extract(self, item, list_article_candidate):
        """Compares the extracted publish dates.

        :param item: The corresponding NewscrawlerItem
        :param list_article_candidate: A list, the list of ArticleCandidate-Objects which have been extracted
        :return: A string, the most likely publish date
        """
        list_publish_date = []

        for article_candidate in list_article_candidate:
            if article_candidate.publish_date != None:
                list_publish_date.append((article_candidate.publish_date, article_candidate.extractor))

        # If there is no value in the list, return None.
        if len(list_publish_date) == 0:
            return None

        # If there are more options than one, return the result from date_extractor.
        list_date_extractor = [x for x in list_publish_date if x[1] == "date_extractor"]
        if len(list_date_extractor) == 0:

            # If there is no date extracted by date_extractor, return the first result of list_publish_date.
            return list_publish_date[0][0]
        else:
            return list_date_extractor[0][0]