Pads vocabulary to a multiple of 'pad' tokens.

        :param vocab: list with vocabulary
        :param pad: integer

def pad_vocabulary(self, vocab, pad):
        """
        Pads vocabulary to a multiple of 'pad' tokens.

        :param vocab: list with vocabulary
        :param pad: integer
        """
        vocab_size = len(vocab)
        padded_vocab_size = (vocab_size + pad - 1) // pad * pad
        for i in range(0, padded_vocab_size - vocab_size):
            token = f'madeupword{i:04d}'
            vocab.append(token)
        assert len(vocab) % pad == 0