Apply agentic searching. (#5196)

### What problem does this PR solve?

#5173

### Type of change

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

rag/nlp/search.py

@@ -15,7 +15,6 @@
 #
 import logging
 import re
-import json
 from dataclasses import dataclass
 
 from rag.settings import TAG_FLD, PAGERANK_FLD
@@ -259,7 +258,7 @@ class Dealer:
         q_denor = np.sqrt(np.sum([s*s for t,s in query_rfea.items() if t != PAGERANK_FLD]))
         for i in search_res.ids:
             nor, denor = 0, 0
-            for t, sc in json.loads(search_res.field[i].get(TAG_FLD, "{}")).items():
+            for t, sc in eval(search_res.field[i].get(TAG_FLD, "{}")).items():
                 if t in query_rfea:
                     nor += query_rfea[t] * sc
                 denor += sc * sc