Fix onnx ptq image prep script for fp16 (#168)

Co-Authored-By: graeb <[email protected]>

Author: kevalmorabia97

examples/onnx_ptq/image_prep.py

@@ -50,6 +50,8 @@ def main():
         calib_tensor.append(transforms(image))
 
     calib_tensor = np.stack(calib_tensor, axis=0)
+    if args.fp16:
+        calib_tensor = calib_tensor.astype(np.float16)  # type: ignore[attr-defined]
     np.save(args.output_path, calib_tensor)