🐛 fix DataclassEncoder bug and add test case

tests/utils.py

@@ -32,6 +32,16 @@ def make_fake_message():
         def image(url: str):
             return FakeMessageSegment("image", {"url": url})
 
+        @staticmethod
+        def node_custom(
+            user_id: str,
+            nickname: str,
+            content: Union["FakeMessage", "FakeMessageSegment", str],
+        ):
+            return FakeMessageSegment(
+                "node", {"user_id": user_id, "nickname": nickname, "content": content}
+            )
+
         def is_text(self) -> bool:
             return self.type == "text"