refine token similarity (#2824)

### What problem does this PR solve?


### Type of change

- [x] Performance Improvement

agent/canvas.py

         convs = []
         for role, obj in self.history[(window_size + 1) * -1:]:
             convs.append({"role": role, "content": (obj if role == "user" else
-                                                    '\n'.join(pd.DataFrame(obj)['content']))})
+                    '\n'.join([str(s) for s in pd.DataFrame(obj)['content']]))})
         return convs
 
     def add_user_input(self, question):

rag/nlp/query.py

                 s += v  # * dtwt[k]
         q = 1e-9
         for k, v in qtwt.items():
-            q += v  # * v
-        #d = 1e-9
-        # for k, v in dtwt.items():
-        #    d += v * v
-        return s / q / max(1, math.sqrt(math.log10(max(len(qtwt.keys()), len(dtwt.keys())))))# math.sqrt(q) / math.sqrt(d)
+            q += v
+        return s / q