Fix filenotfounderror #3056

sentence_transformers/trainer.py

@@ -2,6 +2,7 @@
 
 import logging
 import os
+import warnings
 from collections import OrderedDict
 from contextlib import nullcontext
 from functools import partial
@@ -497,6 +498,19 @@ def _load_best_model(self) -> None:
         if not isinstance(self.model[0], Transformer):
             logger.info("Could not load best model, as the model is not a `transformers`-based model.")
             return
+
+        try:
+            if len(self.model[0].auto_model.active_adapters()):
+                warn_msg = "Could not load best model, as the model has at least one adapter set. Please wait for an update of the transformers library to enable this feature."
+                warnings.warn(
+                    warn_msg,
+                    UserWarning,  # No need to import UserWarning; it's already available
+                    stacklevel=2
+                )
+                logger.info(warn_msg)
+                return
+        except ValueError:
+            pass
 
         try:
             if checkpoint := self.state.best_model_checkpoint: