def is_uninformative(index_list, max_len):
    """
    a boolean function to determine whether an input text is informative or not.
    Since the index 0 is used for padding and the index 1 is used for out-of-vocabulary tokens, when all token indices
    for an input text is either 0 or 1 only (equivalently small than or equal to 1), the text is
    unlikely to be reasonably predicted by the model.

    INPUT:
        index_list: a list of indices
        max_len:  maximum number of tokens in each text
    OUTPUT:
        True or False

    """
    return bool(sum([e <= 1 for e in index_list]) == max_len)