Feat: add use KG to retrieval component. (#5988)

### What problem does this PR solve?

#5973

### Type of change

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

agent/component/retrieval.py

         self.rerank_id = ""
         self.empty_response = ""
         self.tavily_api_key = ""
+        self.use_kg = False
 
     def check(self):
         self.check_decimal_float(self.similarity_threshold, "[Retrieval] Similarity threshold")
                                         self._param.similarity_threshold, 1 - self._param.keywords_similarity_weight,
                                         aggs=False, rerank_mdl=rerank_mdl,
                                         rank_feature=label_question(query, kbs))
+        if self._param.use_kg:
+            ck = settings.kg_retrievaler.retrieval(query,
+                                                   [kbs[0].tenant_id],
+                                                   self._param.kb_ids,
+                                                   embd_mdl,
+                                                   LLMBundle(kbs[0].tenant_id, LLMType.CHAT))
+            if ck["content_with_weight"]:
+                kbinfos["chunks"].insert(0, ck)
+
         if self._param.tavily_api_key:
             tav = Tavily(self._param.tavily_api_key)
             tav_res = tav.retrieve_chunks(query)