docs: def TypeUrlToMessage(type_url):
    """Returns a message instance corresponding to a given type URL."""
  
    if not type_url.startswith(TYPE_URL_PREFIX):
      raise ValueError("Type URL has to start with a prefix %s: %s" %
                       (TYPE_URL_PREFIX, type_url))
  
    full_name = type_url[len(TYPE_URL_PREFIX):]
    try:
      return symbol_database.Default().GetSymbol(full_name)()
    except KeyError as e:
      raise ProtobufTypeNotFound(str(e))