add license

Former-commit-id: 69cfc98d7c81756a5ab6bf962240e393e449fef0

src/llamafactory/train/dpo/trainer.py

@@ -1,3 +1,20 @@
+# Copyright 2024 HuggingFace Inc. and the LlamaFactory team.
+#
+# This code is inspired by HuggingFace's TRL library.
+# https://github.com/huggingface/trl/blob/v0.8.0/trl/trainer/dpo_trainer.py
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 import warnings
 from collections import defaultdict
 from contextlib import nullcontext