code: def get_string(self, key):
          
          if key not in self.all_options:
              kwargs = {}
              if len(self.chain) > 1:
                  kwargs['source'] = Meta(self.all_options, self.chain[-2]).source
              raise BadOptionFormat("Can't find key in options", key=key, chain=self.chain, **kwargs)
  
          # Make sure we special case the "content" option
          if type(key) is str and key.startswith("content."):
              return self.no_format(self.all_options["content"][key[8:]])
          if type(key) is list and len(key) is 2 and key[0] == "content":
              return self.no_format(self.all_options[key])
  
          return super(MergedOptionStringFormatter, self).get_string(key)
docs: Get a string from all_options