code: def disambiguate(names, mark='1'):
      
      names_seen = set()
      new_names = []
      for name in names:
          new_name = name
          while new_name in names_seen:
              new_name += mark
          new_names.append(new_name)
          names_seen.add(new_name)
  
      return new_names
docs: Given a list of strings ``names``, return a new list of names where repeated names have been disambiguated by repeatedly appending the given mark.
  
      EXAMPLE::
  
          >>> disambiguate(['sing', 'song', 'sing', 'sing'])
          ['sing', 'song', 'sing1', 'sing11']