make compatible with py <3.10

lmm_tools/lmm/lmm.py

@@ -4,7 +4,7 @@
 from typing import Optional, Union
 
 
-def encode_image(image: str | Path) -> str:
+def encode_image(image: Union[str, Path]) -> str:
  with open(image, "rb") as f:
  encoded_image = base64.b64encode(f.read()).decode("utf-8")
  return encoded_image