Prevent repeatedly loading the BERT model from the disk. (#37)

* Prevent repeatedly loading the BERT model from the disk.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

text/japanese_bert.py

@@ -4,6 +4,8 @@ import sys
 
 tokenizer = AutoTokenizer.from_pretrained("./bert/bert-base-japanese-v3")
 
+models = dict()
+
 
 def get_bert_feature(text, word2ph, device=None):
     if (
@@ -14,14 +16,15 @@ def get_bert_feature(text, word2ph, device=None):
         device = "mps"
     if not device:
         device = "cuda"
-    model = AutoModelForMaskedLM.from_pretrained("./bert/bert-base-japanese-v3").to(
-        device
-    )
+    if device not in models.keys():
+        models[device] = AutoModelForMaskedLM.from_pretrained(
+            "./bert/bert-base-japanese-v3"
+        ).to(device)
     with torch.no_grad():
         inputs = tokenizer(text, return_tensors="pt")
         for i in inputs:
             inputs[i] = inputs[i].to(device)
-        res = model(**inputs, output_hidden_states=True)
+        res = models[device](**inputs, output_hidden_states=True)
         res = torch.cat(res["hidden_states"][-3:-2], -1)[0].cpu()
     assert inputs["input_ids"].shape[-1] == len(word2ph)
     word2phone = word2ph