def get_publisher_id(xml_soup, issn):
    """Gets the publisher id from the XML. If it can't find one, it returns none. Ultimately it returns a tuple of the issn and the publisher_id"""
    publisher_id = None
    if xml_soup.publisher:
            # if the issn returns a publisher id, print it
            publisher_id = xml_soup.publisher.attrs['id']
            return (issn, publisher_id)
    else:
        # if the issn returns something invalid, ie. nothing in it, return none.
        return (issn, publisher_id)