A Theorem proofs

"} where all tokens in them are uninformative, we have: h So the proof of Lemma 4 is completed. Theorem 1 is also proved. A.2 The proof of Theorem 1 when the encoder is based on Transformer In fact, we only need to prove Lemma 4 because Theorem 1 can be easily derived from it. Beer Reviews Following (Chang et al., 2019; Huang et al., 2021; Y u et al., 2021), we consider a More details are in Table 8. We get the license of Beer Reviews by sending an email to Julian McAuley.