update init to be explicit

Author: isabelizimm

vetiver/__init__.py

@@ -14,6 +14,6 @@
 from .meta import *
 from .write_docker import *
 from .write_fastapi import * 
-from .handlers._interface import create_handler
+from .handlers._interface import create_handler, InvalidModelError
 from .handlers.sklearn import SKLearnHandler
 from .handlers.torch import TorchHandler