Replace assert statement with if condition and ValueError (#13263)

src/transformers/optimization.py

@@ -201,7 +201,8 @@ def get_polynomial_decay_schedule_with_warmup(
     """
 
     lr_init = optimizer.defaults["lr"]
-    assert lr_init > lr_end, f"lr_end ({lr_end}) must be be smaller than initial lr ({lr_init})"
+    if not (lr_init > lr_end):
+        raise ValueError(f"lr_end ({lr_end}) must be be smaller than initial lr ({lr_init})")
 
     def lr_lambda(current_step: int):
         if current_step < num_warmup_steps: