Add reranker for BEIR evaluation (#9743)

* Add reranker for BEIR evaluation

* lower case bm25 query and doc

* cr

llama_index/evaluation/benchmarks/beir.py

@@ -1,11 +1,12 @@
 import os
 from shutil import rmtree
-from typing import Callable, Dict, List
+from typing import Callable, Dict, List, Optional
 
 import tqdm
 
 from llama_index.core import BaseRetriever
-from llama_index.schema import Document
+from llama_index.postprocessor.types import BaseNodePostprocessor
+from llama_index.schema import Document, QueryBundle
 from llama_index.utils import get_cache_dir
 
 
@@ -52,6 +53,7 @@ def run(
         create_retriever: Callable[[List[Document]], BaseRetriever],
         datasets: List[str] = ["nfcorpus"],
         metrics_k_values: List[int] = [3, 10],
+        node_postprocessors: Optional[List[BaseNodePostprocessor]] = None,
     ) -> None:
         from beir.datasets.data_loader import GenericDataLoader
         from beir.retrieval.evaluation import EvaluateRetrieval
@@ -82,6 +84,11 @@ def run(
             results = {}
             for key, query in tqdm.tqdm(queries.items()):
                 nodes_with_score = retriever.retrieve(query)
+                node_postprocessors = node_postprocessors or []
+                for node_postprocessor in node_postprocessors:
+                    nodes_with_score = node_postprocessor.postprocess_nodes(
+                        nodes_with_score, query_bundle=QueryBundle(query_str=query)
+                    )
                 results[key] = {
                     node.node.metadata["doc_id"]: node.score
                     for node in nodes_with_score