[NPU] Support streaming in Python (cpp backend) (#12488)

* Support streaming in NPU Python (cpp backend)

* Small fix

python/llm/src/ipex_llm/transformers/npu_models/convert.py

@@ -314,8 +314,14 @@ def generate(
             new_generate_kwargs[var] = value
 
     if isinstance(inputs[0], torch.Tensor):
+        if streamer is not None:
+            # input ids
+            streamer.put(inputs[0])
         input_list = inputs[0].flatten().tolist()
     else:
+        if streamer is not None:
+            # input ids
+            streamer.put(torch.Tensor(inputs[0]))
         input_list = inputs[0]
     input_length = len(input_list)
 
@@ -335,6 +341,9 @@ def generate(
     from .npu_llm_cpp import run_decode, run_prefill, reset
 
     token = run_prefill(self.model_ptr, input_list, self.vocab_size)
+    if streamer is not None:
+        # 1st tokens
+        streamer.put(torch.tensor([token]))
     idx = 1
     time_t2 = time.perf_counter()
     output_tokens.append(torch.tensor([token]))
@@ -342,12 +351,18 @@ def generate(
         if token == eos:
             break
         token = run_decode(self.model_ptr, token, self.vocab_size)
+        if streamer is not None:
+            # rest tokens
+            streamer.put(torch.tensor([token]))
         idx += 1
         output_tokens.append(torch.tensor([token]))
     output = torch.stack(output_tokens, dim=1)
     output = torch.cat((inputs, output), dim=1)
     time_t3 = time.perf_counter()
 
+    if streamer is not None:
+        streamer.end()
+
     reset(self.model_ptr)
     self.first_cost = time_t2 - time_t1  # seconds
     self.rest_cost_mean = (time_t3 - time_t2) / (idx - 1)  # seconds