make default bm25 params optional

semantic_router/encoders/bm25.py

@@ -9,7 +9,12 @@ class BM25Encoder(BaseEncoder):
     idx_mapping: dict[int, int] | None = None
     type: str = "sparse"
 
-    def __init__(self, name: str = "bm25", score_threshold: float = 0.82):
+    def __init__(
+        self,
+        name: str = "bm25",
+        score_threshold: float = 0.82,
+        use_default_params: bool = True,
+    ):
         super().__init__(name=name, score_threshold=score_threshold)
         try:
             from pinecone_text.sparse import BM25Encoder as encoder
@@ -18,9 +23,15 @@ class BM25Encoder(BaseEncoder):
                 "Please install pinecone-text to use BM25Encoder. "
                 "You can install it with: `pip install semantic-router[hybrid]`"
             )
-        logger.info("Downloading and initializing BM25 model parameters.")
-        self.model = encoder.default()
 
+        self.model = encoder()
+
+        if use_default_params:
+            logger.info("Downloading and initializing default sBM25 model parameters.")
+            self.model = encoder.default()
+            self._set_idx_mapping()
+
+    def _set_idx_mapping(self):
         params = self.model.get_params()
         doc_freq = params["doc_freq"]
         if isinstance(doc_freq, dict):
@@ -53,3 +64,4 @@ class BM25Encoder(BaseEncoder):
         if self.model is None:
             raise ValueError("Model is not initialized.")
         self.model.fit(docs)
+        self._set_idx_mapping()