add support for NVIDIA llm (#1645)

### What problem does this PR solve?

add support for NVIDIA llm
### 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

@@ -462,3 +462,41 @@ class GeminiEmbed(Base):
             title="Embedding of single string")
         token_count = num_tokens_from_string(text)
         return np.array(result['embedding']),token_count
+
+class NvidiaEmbed(Base):
+    def __init__(
+        self, key, model_name, base_url="https://integrate.api.nvidia.com/v1/embeddings"
+    ):
+        if not base_url:
+            base_url = "https://integrate.api.nvidia.com/v1/embeddings"
+        self.api_key = key
+        self.base_url = base_url
+        self.headers = {
+            "accept": "application/json",
+            "Content-Type": "application/json",
+            "authorization": f"Bearer {self.api_key}",
+        }
+        self.model_name = model_name
+        if model_name == "nvidia/embed-qa-4":
+            self.base_url = "https://ai.api.nvidia.com/v1/retrieval/nvidia/embeddings"
+            self.model_name = "NV-Embed-QA"
+        if model_name == "snowflake/arctic-embed-l":
+            self.base_url = "https://ai.api.nvidia.com/v1/retrieval/snowflake/arctic-embed-l/embeddings"
+
+    def encode(self, texts: list, batch_size=None):
+        payload = {
+            "input": texts,
+            "input_type": "query",
+            "model": self.model_name,
+            "encoding_format": "float",
+            "truncate": "END",
+        }
+        res = requests.post(self.base_url, headers=self.headers, json=payload).json()
+        return (
+            np.array([d["embedding"] for d in res["data"]]),
+            res["usage"]["total_tokens"],
+        )
+
+    def encode_queries(self, text):
+        embds, cnt = self.encode([text])
+        return np.array(embds[0]), cnt