:param keys: list of str to sort by, if name starts with -
            reverse order
        :return: None

def sort_by_key(self, keys=None):
        """
        :param keys: list of str to sort by, if name starts with -
            reverse order
        :return: None
        """
        keys = keys or self.key_on
        keys = keys if isinstance(keys, (list, tuple)) else [keys]
        for key in reversed(keys):
            reverse, key = (True, key[1:]) if key[0] == '-' else (False, key)
            self.table.sort(key=lambda row: row[key], reverse=reverse)