export bf16 (#618)

Author: lucylq

export_et.py

@@ -79,6 +79,9 @@ def export_model(model, device, output_path, args=None) -> str:  # noqa: C901
         if state_dict_dtype != torch.float32:
             print("model.to torch.float32")
             model = model.to(dtype=torch.float32)
+    elif target_precision == torch.bfloat16:
+            print("model.to torch.bfloat16")
+            model = model.to(dtype=torch.bfloat16)
     else:
         raise ValueError(f"Unsupported dtype for ET export: {target_precision}")