code: def bibcode_from_url(cls, url):
          
          try:
              code = url.split('/abs/')
              code = code[1].strip()
              return code
          except:
              return None
docs: Given a URL, try to find the ADS bibcode.
  
          Currently: only `ads` URLs will work, e.g.
  
          Returns
          -------
          code : str or 'None'
              The Bibcode if found, otherwise 'None'