Fix is_dataclass typing issue

src/requestmodel/fastapi.py

@@ -8,7 +8,7 @@
 import types
 from collections import defaultdict
 from collections import deque
-from dataclasses import is_dataclass
+from dataclasses import is_dataclass, dataclass
 from decimal import Decimal
 from enum import Enum
 from ipaddress import IPv4Address
@@ -168,7 +168,7 @@ def jsonable_encoder(  # noqa: C901
             exclude_defaults=exclude_defaults,
             sqlalchemy_safe=sqlalchemy_safe,
         )
-    if dataclasses.is_dataclass(obj):
+    if dataclasses.is_dataclass(obj) and not isinstance(obj, type):
         obj_dict = dataclasses.asdict(obj)
         return jsonable_encoder(
             obj_dict,