Deprecate BestOfNSampler (#4291)

Co-authored-by: behroozazarkhalili <ermiaazarkhalili>
Co-authored-by: Behrooz Azarkhalili <80390531+behroozazarkhalili@users.noreply.github.com>

docs/source/best_of_n.md

@@ -1,5 +1,8 @@
 # Best of N sampling: Alternative ways to get better model output without RL based fine-tuning
 
+> [!WARNING]
+> Best-of-N sampling is deprecated and will be removed in TRL 0.25.0.
+
 Within the extras module is the `best-of-n` sampler class that serves as an alternative method of generating better model output.
 As to how it fares against the RL based fine-tuning, please look in the `examples` directory for a comparison example
 

trl/extras/best_of_n_sampler.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import warnings
 from typing import Any, Callable, Optional, Union
 
 import torch
@@ -42,8 +43,16 @@ class BestOfNSampler:
         generation_config ([`~transformers.GenerationConfig`], *optional*):
             Generation config passed to the underlying model's `generate` method. See
             [`~transformers.GenerationConfig`] for more details.
+
+    <Deprecated version="0.24.0">
+
+    `BestOfNSampler` is deprecated and will be removed in version 0.25.
+
+    </Deprecated>
     """
 
+    warnings.warn("`BestOfNSampler` is deprecated and will be removed in TRL 0.25.", FutureWarning, stacklevel=2)
+
     def __init__(
         self,
         model: PreTrainedModelWrapper,