feat: Add ColBERT late interaction model support (#33686)

Signed-off-by: Ilya Boytsov <ilyaboytsov1805@gmail.com>
Signed-off-by: Ilya Boytsov <boytsovpanamera@mail.ru>
Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>
Co-authored-by: wang.yuqi <yuqi.wang@daocloud.io>

examples/pooling/score/colbert_rerank_online.py

@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""
+Example of using ColBERT late interaction model for reranking.
+
+ColBERT (Contextualized Late Interaction over BERT) uses per-token embeddings
+and MaxSim scoring for document reranking, providing better accuracy than
+single-vector models while being more efficient than cross-encoders.
+
+Start the server with:
+    vllm serve answerdotai/answerai-colbert-small-v1
+
+Then run this script:
+    python colbert_rerank_online.py
+"""
+
+import json
+
+import requests
+
+url = "http://127.0.0.1:8000/rerank"
+
+headers = {"accept": "application/json", "Content-Type": "application/json"}
+
+data = {
+    "model": "answerdotai/answerai-colbert-small-v1",
+    "query": "What is machine learning?",
+    "documents": [
+        "Machine learning is a subset of artificial intelligence.",
+        "Python is a programming language.",
+        "Deep learning uses neural networks for complex tasks.",
+        "The weather today is sunny.",
+    ],
+}
+
+
+def main():
+    response = requests.post(url, headers=headers, json=data)
+
+    if response.status_code == 200:
+        print("ColBERT Rerank Request successful!")
+        result = response.json()
+        print(json.dumps(result, indent=2))
+
+        # Show ranked results
+        print("\nRanked documents (most relevant first):")
+        for item in result["results"]:
+            doc_idx = item["index"]
+            score = item["relevance_score"]
+            print(f"  Score {score:.4f}: {data['documents'][doc_idx]}")
+    else:
+        print(f"Request failed with status code: {response.status_code}")
+        print(response.text)
+
+
+if __name__ == "__main__":
+    main()