Add usage

Signed-off-by: junjie.jiang <junjie.jiang@zilliz.com>

s_bert.py

@@ -77,7 +77,7 @@ class STransformers(NNOperator):
     Operator using pretrained Sentence Transformers
     """
 
-    def __init__(self, model_name: str = None, device: str = None):
+    def __init__(self, model_name: str = None, device: str = None, return_usage: bool = False):
         self.model_name = model_name
         if device is None:
             device = 'cuda' if torch.cuda.is_available() else 'cpu'
@@ -87,6 +87,7 @@ class STransformers(NNOperator):
         else:
             log.warning('The operator is initialized without specified model.')
         self._tokenize = self.get_tokenizer()
+        self.return_usage = return_usage
 
     def __call__(self, txt: Union[List[str], str]):
         if isinstance(txt, str):
@@ -94,11 +95,14 @@ class STransformers(NNOperator):
         else:
             sentences = txt
         inputs = self._tokenize(sentences)
+        num_tokens = int(torch.count_nonzero(inputs['input_ids']))
         embs = self.model(**inputs).cpu().detach().numpy()
         if isinstance(txt, str):
             embs = embs.squeeze(0)
         else:
             embs = list(embs)
+        if self.return_usage:
+            return {'data': embs, 'token_usage': num_tokens}
         return embs
 
     @property