add support for LM Studio (#1663)

### What problem does this PR solve?

#1602 

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Zhedong Cen <cenzhedong2@126.com>

rag/llm/embedding_model.py

@@ -500,3 +500,24 @@ class NvidiaEmbed(Base):
     def encode_queries(self, text):
         embds, cnt = self.encode([text])
         return np.array(embds[0]), cnt
+
+
+class LmStudioEmbed(Base):
+    def __init__(self, key, model_name, base_url):
+        if not base_url:
+            raise ValueError("Local llm url cannot be None")
+        if base_url.split("/")[-1] != "v1":
+            self.base_url = os.path.join(base_url, "v1")
+        self.client = OpenAI(api_key="lm-studio", base_url=self.base_url)
+        self.model_name = model_name
+
+    def encode(self, texts: list, batch_size=32):
+        res = self.client.embeddings.create(input=texts, model=self.model_name)
+        return (
+            np.array([d.embedding for d in res.data]),
+            1024,
+        )  # local embedding for LmStudio donot count tokens
+
+    def encode_queries(self, text):
+        res = self.client.embeddings.create(text, model=self.model_name)
+        return np.array(res.data[0].embedding), 1024