fix import ipex problem (#9323)

* fix import ipex problem

* fix style

python/llm/src/bigdl/llm/transformers/models/llama.py

@@ -59,21 +59,23 @@ def repeat_kv(hidden_states: torch.Tensor, n_rep: int) -> torch.Tensor:
 KV_CACHE_ALLOC_BLOCK_LENGTH = 256
 
 
-def get_ipex_version():
+_ipex_version = None
 
-    if importlib.util.find_spec("intel_extension_for_pytorch") is not None:
-        import intel_extension_for_pytorch as ipex
-        return ipex.__version__
-    else:
-        return None
 
+def get_ipex_version():
+
+    global _ipex_version
+    if _ipex_version is not None:
+        return _ipex_version
 
-ipex_version = get_ipex_version()
+    import intel_extension_for_pytorch as ipex
+    _ipex_version = ipex.__version__
+    return _ipex_version
 
 
 def llama_rms_norm_forward(self, hidden_states):
     if hidden_states.device.type == "xpu" and not (self.training and hidden_states.requires_grad):
-        if ipex_version == "2.0.110+xpu":
+        if get_ipex_version() == "2.0.110+xpu":
             hidden_states, _ = torch.ops.torch_ipex.rms_norm(hidden_states,
                                                              [self.weight.size(0)], self.weight)
         else: