2 files changed, 7 insertions, 4 deletions

diff --git a/g4f/providers/base_provider.py b/g4f/providers/base_provider.py
index 685a6f98..5624c9e1 100644
--- a/g4f/providers/base_provider.py
+++ b/g4f/providers/base_provider.py
@@ -271,13 +271,13 @@ class AsyncGeneratorProvider(AsyncProvider):
         raise NotImplementedError()
 
 class ProviderModelMixin:
-    default_model: str
+    default_model: str = None
     models: list[str] = []
     model_aliases: dict[str, str] = {}
 
     @classmethod
     def get_models(cls) -> list[str]:
-        if not cls.models:
+        if not cls.models and cls.default_model is not None:
             return [cls.default_model]
         return cls.models
 
diff --git a/g4f/providers/helper.py b/g4f/providers/helper.py
index 0ec9aac2..7ebe0d02 100644
--- a/g4f/providers/helper.py
+++ b/g4f/providers/helper.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 import random
 import string
 
-from ..typing import Messages
+from ..typing import Messages, Cookies
 
 def format_prompt(messages: Messages, add_special_tokens=False) -> str:
     """
@@ -56,4 +56,7 @@ def filter_none(**kwargs) -> dict:
         key: value
         for key, value in kwargs.items()
         if value is not None
-    }
\ No newline at end of file
+    }
+
+def format_cookies(cookies: Cookies) -> str:
+    return "; ".join([f"{k}={v}" for k, v in cookies.items()])
\ No newline at end of file