Put BaseModel in quotes

Contributes to CURA-7180

cura/OAuth2/KeyringAttribute.py

@@ -27,7 +27,7 @@ class KeyringAttribute:
     """
     Descriptor for attributes that need to be stored in the keyring. With Fallback behaviour to the preference cfg file
     """
-    def __get__(self, instance: BaseModel, owner: type) -> Optional[str]:
+    def __get__(self, instance: "BaseModel", owner: type) -> Optional[str]:
         if self._store_secure:  # type: ignore
             try:
                 value = keyring.get_password("cura", self._keyring_name)
@@ -39,7 +39,7 @@ class KeyringAttribute:
         else:
             return getattr(instance, self._name)
 
-    def __set__(self, instance: BaseModel, value: Optional[str]):
+    def __set__(self, instance: "BaseModel", value: Optional[str]):
         if self._store_secure:
             setattr(instance, self._name, None)
             try: