feat: add answerdotai rerankers support and minor improvements (#1560)

This PR:
- Adds missing license headers
- Integrates with answerdotai Rerankers package
- Updates ColbertReranker to subclass answerdotai package. This is done
to keep backwards compatibility as some users might be used to importing
ColbertReranker directly
- Set `trust_remote_code` to ` True` by default in CrossEncoder and
sentence-transformer based rerankers

python/python/tests/test_rerankers.py

@@ -15,6 +15,7 @@ from lancedb.rerankers import (
     CrossEncoderReranker,
     OpenaiReranker,
     JinaReranker,
+    AnswerdotaiRerankers,
 )
 from lancedb.table import LanceTable
 
@@ -254,12 +255,20 @@ def test_cross_encoder_reranker(tmp_path, use_tantivy):
 
 @pytest.mark.parametrize("use_tantivy", [True, False])
 def test_colbert_reranker(tmp_path, use_tantivy):
-    pytest.importorskip("transformers")
+    pytest.importorskip("rerankers")
     reranker = ColbertReranker()
     table, schema = get_test_table(tmp_path, use_tantivy)
     _run_test_reranker(reranker, table, "single player experience", None, schema)
 
 
+@pytest.mark.parametrize("use_tantivy", [True, False])
+def test_answerdotai_reranker(tmp_path, use_tantivy):
+    pytest.importorskip("rerankers")
+    reranker = AnswerdotaiRerankers()
+    table, schema = get_test_table(tmp_path, use_tantivy)
+    _run_test_reranker(reranker, table, "single player experience", None, schema)
+
+
 @pytest.mark.skipif(
     os.environ.get("OPENAI_API_KEY") is None, reason="OPENAI_API_KEY not set"
 )