class Github::PageIterator

def prev
  return nil unless prev_page_uri
  params   = parse_query prev_page_uri.split(QUERY_STR_SEP).last
  params['page'] = parse_page_number(prev_page_uri)
  params['per_page'] = parse_per_page_number(prev_page_uri)
  response = page_request prev_page_uri.split(QUERY_STR_SEP).first, params
  update_page_links response.links
  response
end