code: def get(self, fragment_info):
          
          if not self.is_cached(fragment_info):
              raise KeyError(u"Attempt to get text not cached")
          return self.cache[fragment_info]
docs: Get the value associated with the given key.
  
          :param fragment_info: the text key
          :type  fragment_info: tuple of str ``(language, text)``
          :raises: KeyError if the key is not present in the cache