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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def backfill_unk_emb(self, E, filled_words):
 """ Backfills an embedding matrix with the embedding for the unknown token. :param E: original embedding matrix of dimensions `(vocab_size, emb_dim)`. :param filled_words: these words will not be backfilled with unk. NOTE: this function is for internal use. """

        unk_emb = E[self[self._unk]]
        for i, word in enumerate(self):
            if word not in filled_words:
                E[i] = unk_emb