code: def from_config(cls, filename):
          
          import telegram
          d = load_config_file(filename)
          request = cls.get_proxy_request(d) if 'proxy_url' in d else None
  
          if 'token' in d and 'chat_id' in d:
              bot = telegram.Bot(d['token'], request=request)
              obs = cls(bot, **d)
          else:
              raise ValueError("Telegram configuration file must contain "
                               "entries for 'token' and 'chat_id'!")
          for k in ['completed_text', 'interrupted_text', 'failed_text']:
              if k in d:
                  setattr(obs, k, d[k])
          return obs
docs: Create a TelegramObserver from a given configuration file.
  
          The file can be in any format supported by Sacred
          (.json, .pickle, [.yaml]).
          It has to specify a ``token`` and a ``chat_id`` and can optionally set
          ``silent_completion``,``completed_text``, ``interrupted_text``, and
          ``failed_text``.