leaderboard collation and template, but not working right

app.py

@@ -237,8 +237,56 @@ def create_app(config=Config):
         }
         mongo.db.users.insert_one(admin_user)
         print(f"Admin {username} added! Referral code is {admin_user['referral_code']}")
+    
+    @app.route('/leaderboard')
+    def leaderboard():
+        leaders = mongo.db.pins.aggregate([
+            {
+                "$group": {
+                    "_id":"$added_by",
+                    "count": {"$sum":1}
+                }
+            },
+            {
+                "$sort": {"count":-1}
+            },
+            {
+                "$limit":10
+            },
+            {
+                "$lookup": {
+                    "from": "users",
+                    "localField": "_id",
+                    "foreignField": "_id",
+                    "as": "user_info"
+                }
+            },
+            {
+                "$unwind": "$user_info"
+            },
+            {
+            "$project": {
+                "_id":0,
+                "added_by": "$_id",
+                "count":1,
+                "username": "$user_info.username"
+            }
+            }
+        ])
+        print(leaders)
+        for leader in leaders:
+            leader["username"] = leader["username"][0]+"***"+leader["username"][-1]
+        if current_user.is_authenticated:
+            username = user.username
+        else:
+            username = None
+        return render_template('leaderboard.html', leaders=leaders, username=username)
+        
+    
     return app
 
+    
+
 app=create_app()
 if __name__ == '__main__':
     app.run(debug=True)

templates/leaderboard.html

@@ -0,0 +1,6 @@
+{% extends 'secondbase.html' %}
+<ul>
+{% for leader in leaders %}
+    {% if username != None and leader.username == username %}<li><span style="padding-left: -100%;">¡Felicidades, estás aquí!</span><b>{{ leader.username }} -> {{leader.count}}</b></li>{% else %}{{leader.username}} -> {{leader.count}}{% endif %}
+{% endfor %}
+</ul>