[RAG] Clean Rag readme in examples (#7413)

* Improve README + consolidation script

* Reformat README

* Reformat README

Co-authored-by: Your Name <you@example.com>

examples/rag/consolidate_rag_checkpoint.py

@@ -0,0 +1,99 @@
+"""
+A script creating a RAG checkpoint from a generator and a question encoder checkpoints.
+"""
+
+import argparse
+from pathlib import Path
+
+from transformers import AutoConfig, AutoTokenizer, RagConfig, RagSequenceForGeneration, RagTokenForGeneration
+
+
+def consolidate(
+    model_type,
+    generator_name_or_path: str,
+    question_encoder_name_or_path: str,
+    dest_dir: Path,
+    config_name_or_path: str = None,
+    generator_tokenizer_name_or_path: str = None,
+    question_encoder_tokenizer_name_or_path: str = None,
+):
+
+    if config_name_or_path is None:
+        config_name_or_path = "facebook/rag-token-base" if model_type == "rag_token" else "facebook/rag-sequence-base"
+
+    if generator_tokenizer_name_or_path is None:
+        generator_tokenizer_name_or_path = generator_name_or_path
+
+    if question_encoder_tokenizer_name_or_path is None:
+        question_encoder_tokenizer_name_or_path = question_encoder_name_or_path
+
+    model_class = RagTokenForGeneration if model_type == "rag_token" else RagSequenceForGeneration
+
+    # Save model.
+    rag_config = RagConfig.from_pretrained(config_name_or_path)
+    gen_config = AutoConfig.from_pretrained(generator_name_or_path)
+    question_encoder_config = AutoConfig.from_pretrained(question_encoder_name_or_path)
+
+    rag_config.generator = gen_config
+    rag_config.question_encoder = question_encoder_config
+
+    rag_model = model_class.from_pretrained_question_encoder_generator(
+        question_encoder_name_or_path, generator_name_or_path, config=rag_config
+    )
+    rag_model.save_pretrained(dest_dir)
+
+    # Sanity check.
+    model_class.from_pretrained(dest_dir)
+
+    # Save tokenizers.
+    gen_tokenizer = AutoTokenizer.from_pretrained(generator_tokenizer_name_or_path)
+    gen_tokenizer.save_pretrained(dest_dir / "generator_tokenizer/")
+    question_encoder_tokenizer = AutoTokenizer.from_pretrained(question_encoder_tokenizer_name_or_path)
+    question_encoder_tokenizer.save_pretrained(dest_dir / "question_encoder_tokenizer/")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--model_type",
+        choices=["rag_sequence", "rag_token"],
+        required=True,
+        type=str,
+        help="RAG model type: rag_sequence, rag_token",
+    )
+    parser.add_argument("--dest", type=str, required=True, help="Path to the output checkpoint directory.")
+    parser.add_argument("--generator_name_or_path", type=str, required=True, help="Generator model identifier")
+    parser.add_argument(
+        "--question_encoder_name_or_path", type=str, required=True, help="Question encoder model identifier"
+    )
+
+    parser.add_argument(
+        "--generator_tokenizer_name_or_path",
+        type=str,
+        help="Generator tokenizer identifier, if not specified, resolves to ``generator_name_or_path``",
+    )
+    parser.add_argument(
+        "--question_encoder_tokenizer_name_or_path",
+        type=str,
+        help="Question encoder tokenizer identifier, if not specified, resolves to ``question_encoder_name_or_path``",
+    )
+    parser.add_argument(
+        "--config_name_or_path",
+        type=str,
+        help="Identifier of the model config to use, if not provided, resolves to a base config for a given ``model_type``",
+    )
+
+    args = parser.parse_args()
+
+    dest_dir = Path(args.dest)
+    dest_dir.mkdir(exist_ok=True)
+
+    consolidate(
+        args.model_type,
+        args.generator_name_or_path,
+        args.question_encoder_name_or_path,
+        dest_dir,
+        args.config_name_or_path,
+        args.generator_tokenizer_name_or_path,
+        args.question_encoder_tokenizer_name_or_path,
+    )