fix json serialization

app.py

@@ -1,5 +1,6 @@
 import json
 from typing import Literal
+from datetime import datetime
 
 import gradio as gr
 from huggingface_hub import list_models, model_info, hf_hub_download
@@ -106,10 +107,10 @@ def get_model_info(model_id: str) -> dict:
             result["author"] = model.author
 
         if hasattr(model, "created_at") and model.created_at is not None:
-            result["created_at"] = model.created_at
+            result["created_at"] = str(model.created_at)
 
         if hasattr(model, "last_modified") and model.last_modified is not None:
-            result["last_modified"] = model.last_modified
+            result["last_modified"] = str(model.last_modified)
 
         if hasattr(model, "downloads") and model.downloads is not None:
             result["downloads"] = model.downloads
@@ -146,10 +147,26 @@ def get_model_info(model_id: str) -> dict:
                 result["datasets"] = model.card_data.datasets
 
         if hasattr(model, "siblings") and model.siblings is not None:
-            result["siblings"] = model.siblings
+            result["siblings"] = []
+            for s in model.siblings:
+                if isinstance(s, str):
+                    result["siblings"].append(s)
+                else:
+                    result["siblings"].append({
+                        k: str(v) if isinstance(v, datetime) else v 
+                        for k, v in s.__dict__.items() if not k.startswith('_')
+                    })
 
         if hasattr(model, "spaces") and model.spaces is not None:
-            result["spaces"] = model.spaces
+            result["spaces"] = []
+            for s in model.spaces:
+                if isinstance(s, str):
+                    result["spaces"].append(s)
+                else:
+                    result["spaces"].append({
+                        k: str(v) if isinstance(v, datetime) else v 
+                        for k, v in s.__dict__.items() if not k.startswith('_')
+                    })
 
         if hasattr(model, "xet_enabled") and model.xet_enabled is not None:
             result["xet_enabled"] = model.xet_enabled