def get_next_page_link(links, index=1):
    """
    Get the next page url of github from the response header
    returns none if the response do not contain next page
    """

    link_list = links.split(',')
    for link in link_list:
        if 'rel="next"' in link:
            next_link= link.split('>;')[0][index:]
            return next_link
    return None