Update tone_sandhi.py

paddlespeech/t2s/frontend/tone_sandhi.py

@@ -268,7 +268,7 @@ class ToneSandhi():
         for (word, pos) in seg:
             orig_finals = lazy_pinyin(
                 word, neutral_tone_with_five=True, style=Style.FINALS_TONE3)
-            # after pypinyin==0.41.0, 嗯 will be processed as "", so we need to change it to "n2"
+            # after pypinyin==0.44.0, '嗯' need to be n2, cause the initial and final consonants cannot be empty at the same time
             en_index = [index for index, c in enumerate(word) if c == "嗯"]
             for i in en_index:
                 orig_finals[i] = "n2"