diff --git a/django-stubs/contrib/sessions/backends/base.pyi b/django-stubs/contrib/sessions/backends/base.pyi
index 58deb72..5fcb05e 100644
--- a/django-stubs/contrib/sessions/backends/base.pyi
+++ b/django-stubs/contrib/sessions/backends/base.pyi
@@ -1,8 +1,6 @@
 from datetime import datetime
 from typing import Any, Dict, Optional, Union
 
-from django.db.models.base import Model
-
 VALID_KEY_CHARS: Any
 
 class CreateError(Exception): ...
@@ -18,8 +16,8 @@ class SessionBase(Dict[str, Any]):
     def set_test_cookie(self) -> None: ...
     def test_cookie_worked(self) -> bool: ...
     def delete_test_cookie(self) -> None: ...
-    def encode(self, session_dict: Dict[str, Model]) -> str: ...
-    def decode(self, session_data: Union[bytes, str]) -> Dict[str, Model]: ...
+    def encode(self, session_dict: Dict[str, Any]) -> str: ...
+    def decode(self, session_data: Union[bytes, str]) -> Dict[str, Any]: ...
     def has_key(self, key: Any): ...
     def keys(self): ...
     def values(self): ...
@@ -33,7 +31,7 @@ class SessionBase(Dict[str, Any]):
     def get_expire_at_browser_close(self) -> bool: ...
     def flush(self) -> None: ...
     def cycle_key(self) -> None: ...
-    def exists(self, session_key: str) -> None: ...
+    def exists(self, session_key: str) -> bool: ...
     def create(self) -> None: ...
     def save(self, must_create: bool = ...) -> None: ...
     def delete(self, session_key: Optional[Any] = ...) -> None: ...